Ahaan's Notes

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Physics Notes
1. General Physics:
i)
Length and Time:
a) Use of rules and measuring cylinders to find length or volume:
- Rulers used to measure distances from millimeters up to a meter
- Caliper used if ruler cannot be placed next to object
- Tapes used for greater distance
- Change in volume in measuring cylinder following addition of object is equal to
volume of object
b) Micrometer screw gauge:
- Revolving barrel with extra scale which opens by one unit each time
- Closed at point where object fits in perfectly
c) Use of clocks and devices:
- Use automatic timings to reduce human error
d) Average value for small timings:
- Can take reading of values based on large number of occurrence and divide
- Example is pendulum time period
ii)
Motion:
a) Speed:
- Distance moved upon time taken
b) Velocity and speed difference:
- Speed is ignorant of direction, velocity is speed as well as direction of travel
c) Acceleration:
Acceleration is equal to change in velocity upon time taken
d) Skill based
e) Speed from DT graph:
- Gradient
f) Skill based
g) Skill based
h) Skill based
i) Skill based
j) Skill based
k) Skill based
l) Acceleration for body near Earth:
- Constant acceleration
- 9.8m/s2 (10)
- G = 2h/t2
m) Effect of air resistance:
- With air resistance, lighter objects are slowed down a lot more while falling
- Without, different weights fall at the same speed
iii)
Mass and weight:
a) Mass:
- Amount of matter in an object
b) Mass as resistance:
iv)
v)
- Mass resists changes in motion
- Greater object offers greater resistance to starting to move, as well as stopping
c) Weight:
- Force of gravity pulling on/exerted on mass (measured in KG not N)
d) Difference between mass and weight (done)
e) W = mg
f) Weight as effect of gravitational field (done)
g) Skill based
Density:
a) p = m/v
b) Experiment of liquid and regularly shaped solid:
- Volume found using measuring cylinder for liquid or formula for solid
- Mass found using balance
- Mass/volume gives density
c) Irregular solid:
- Add to liquid and measure change in volume
d) Denser object (relative to liquid) sinks, less dense floats
Effects of forces:
a) Force:
- Push or pull exerted by one object on another
- Force may produce change in size or shape of body
b) Extension-load graphs:
- Greater force caused greater spring extension, greater reading
c) Hooke’s Law:
- Beneath elastic limit, extension is proportional to load
- F = kx (k is spring constant)
d) Limit of proportionality:
- Point at which material no longer obeys Hooke’s Law and extension is not
proportionate
e) Force changing motion:
- Takes force to get object at rest to move, takes force to change speed or
direction
- Resistance to change is inertia
- Greater mass, greater inertia
f) Acceleration (including direction) = Force/Mass
g) Skill based
h) Circular motion:
- To make object follow circular path, inward/centripetal force is needed
- Force always acts towards centre of circle
Since object is always changing velocity, it is always accelerating (result of
change in direction)
i) No resultant force causes rest or constant speed in straight line
j) Friction:
- Force resisting relative motion of two surfaces
-
vi)
vii)
viii)
ix)
x)
Leads to heating effect
Can be static (resistance to beginning movement) or dynamic (moving)
Wastes energy (converted to heat energy and lost)
Advantages are giving shoes and tires grip on the ground, and braking systems
Disadvantages are that it prevents machinery from moving freely, and heats up
moving parts
e) Air resistance is form of friction
Turning effect:
a) Moment of force:
- Turning effect force
- Used in wrench, opening a door, levers
b) Increasing force/distance from pivot increased moment
c) Moment= product force x perpendicular distance from pivot
d) Skill based
e) Skill based
Conditions for Equilibrium:
a) Equilibrium situation:
- No resultant force (upward = downward)
- No resultant turning effect (clockwise = anticlockwise)
b) Experiment:
- Balancing a beam
Centre of Mass:
a) Experiment to find centre of mass of plane lamina:
- Make holes in corners
- Draw lines straight down
- Point where lines meet is centre of mass
b) Effect of Position of Centre of Mass on Stability:
- If line drawn straight down from centre of mass passes through base, object will
not fall
- Wider base increases stability
- Three types of equilibrium: Stable, Unstable, Neutral
Scalars and Vectors:
a) Vectors have magnitude and direction, as opposed to just magnitude
b) Examples of scalar-vector:
- Scalar: Time, volume, speed, temperature, mass, electric charge
- Vector: Force, weight, velocity, acceleration, momentum
c) Determine result of two vectors:
- Parallelogram: Complete parallelogram, diagonal from origin is sum
- Triangle: Find two sides touching tales, third side in opposite direction is sum
- Can resolve vector into components at right angles
- Can use trigonometry to solve
Momentum and Impulse:
a) Concepts:
- Momentum is tendency of object to keep moving in same direction
xi)
xii)
- Impulse is measure of how much force changes momentum of an object
b) Equation for Momentum:
- Momentum = mass x velocity
c) Equation for Impulse:
- Ft = mv – mu
d) Skill based
Energy:
a) Identify changes in energy:
- Kinetic energy: Energy due to motion, all moving objects have it
- Gravitational potential: Energy due to force acting against gravity
- Elastic potential energy: Energy due to change in shape, present in stretched
rubber band or compressed spring
- Chemical potential energy: Energy stored in fuel, batteries, or food
- Nuclear potential energy: Energy present due to fore holding together atom
- Internal energy: Energy present in all atoms and molecules due to random
motion and position
b) Equations:
- KE = ½ x mv2
- PE = mgh
c) Energy is transferred and transformed by various methods:
- Forces/mechanical working: Running, moving an object, stretching a spring
- Electrical currents: Bulbs, Electrical items
- Heating: Splitting an atom
- Waves: Energy transferred through electromagnetic, sound, and water waves
d) Skill based
e) Skill based
f) Dissipation of Energy:
- Energy spread out among objects and surroundings over events
- Greater dissipation, lower efficiency
Energy resources:
I.
Obtaining Electricity:
- Chemical energy stored in fuel: Fuels are burnt to give heat energy, this turns
into heat energy in water, then kinetic energy in turbine, then electrical energy
in generator
- Water: Kinetic energy from water turns a turbine which turns a generator which
produces electrical energy (Tidal energy forms artificial lake through damning
estuary and generator is turned through filling and emptying, waves cause up
and down movement on surface which can be used to drive generators,
hydroelectric is from artificial lake formed behind a dam which turns turbines
and then generators when it rushes down)
- Geothermal resources: Thermal energy heats water, water turns into steam,
thermal energy of steam turns turbine which then has kinetic energy, which
turns generator which produces electrical energy
-
II.
III.
IV.
V.
Nuclear energy: Splitting of nuclei releases thermal energy, heats water to
steam, turns turbines with kinetic energy and becomes electric in generators
- Solar energy: Solar panels absorb energy radiated by sun and use it to heat
water for turbines or direct use, solar cells convert light energy into electrical
energy
- Wind energy: Kinetic energy from wind turns a turbine which turns a generator
which produces energy
Sun as source for all energy except geothermal, nuclear, and tide:
- Chemical: Sun gives energy to plants, plants convert it into water and carbon
dioxide for growth, animals eat plants to get energy, plants and animals die to
form fossil fuels through intense pressure, fossils fuels used for energy
- Waves: Waves are caused by wind, wind is caused by heated air rising above the
equator, heat provided by sun
- Hydroelectric: Artificial lakes kept full by river water formed by rain or snow,
weather conditions caused by sun
- Solar panels and cells: Obvious
- Wind: Wind caused by sun
- Geothermal: Thermal energy under the Earth’s surface caused by radioactive
material, not sun
- Nuclear energy: Caused by nuclei of uranium, not sun
- Tides: Gravitational pull of mon creates gentle bulges in Earth’s oceans, Earth’s
rotation causes high and low tides as they pass in and out of the bulges, motion
causes energy, not sun
Sun as nuclear fusion:
- Energy of sun released by light nuclei (fusion)
Advantages and disadvantages of each method:
Method
R?
Cost
Reliability
Scal
e
High
Fossil
Fuels
N
Low
High
Tidal
R
R
Hydroelectric
R
High as
easy to
predict tide
Not high,
wave size
varies
Very
reliable
High
Wave
Initial
cost
high
Initial
cost
high
Initial
cost
high
Geothermal
R
High
Reliable
Very Not damaging
high
Not
very
high
High
Environmental
Impact
Gives off
damaging
pollutants
Affects ecosystem
surrounding dam
Other
Affects
transport
system
Not damaging
Can damage
ecosystem, could
cause floods
D
D
Price
unstable,
limited
reservoirs
Difficult to
find
Nuclear
R
Solar
R
Very
high
High
Very Potentially very
high damaging
Many
waste
products
Need to
be large
to work
Large area
needed,
are noisy
Initial LowHigh Not damaging
cost
depends
high
on weather
Wind
R
Initial LowHigh Not damaging
cost
depends
high
on weather
VI.
Understand efficiency qualitatively:
- Some energy is always transformed into other forms, such as sound or heat
- Therefore efficiency is used to see how much of the total power output (input) is
in useful form
VII.
Use equation:
- Efficiency = useful energy output/energy input or output x 100
xiii)
Work:
a) Work done = energy transformed or transferred
b) Work = Force x Distance Moved
xiv)
Power:
a) Power = Work done (energy transferred)/Time taken
xv)
Pressure:
a) Pressure = Force/Area
b) Relate pressure to force and area:
- Studs on football boots have small area of contact to put pressure on ground and
sink in for extra grip
- Area under knife’s blade is very small to put pressure on material and cut
- Area under drawing pin is small to put pressure on wood
- Skis have large area
c) Mercury Barometer:
- Device used to measure atmospheric pressure (the weight of air in the
atmosphere)
- Made of glass, consists of upside down tube, base of tube dips into beaker below
surface of Mercury
- Atmospheric pressure pushes down the mercury in beaker, which pushes up the
mercury in tube
- As tube is vacuum, there is no resistance, and atmospheric pressure pushes it up
until column of mercury balances pressure (height is used as measure)
d) Pressure beneath liquid surface to depth and density:
- Pressure acts equally in all directions
- Pressure does not depend on shape or width of container
- Pressure increases with depth (Deeper into a liquid you go, greater the weight of
liquid above and higher the pressure)
- Pressure depends on density of liquid (greater density, greater pressure)
e) Use equation p = hpg:
- To calculate pressure, weight is needed
f)
Mass = density x volume (pAh), weight = pgAh, therefore force on base = Density
x Gravity x Height/Area, therefore pressure = Density x Gravity x Height
Use and describe use of manometer:
- One end of manometer is connected to air, one end to gas being measured
- If there is pressure difference between ends, mercury column is uneven
2. Thermal Physics:
i)
ii)
iii)
States of Matter:
a) Distinguishing properties of solids, liquids and gases:
- Solid has fixed volume, high density, definite shape, and does not flow
- Liquid has fixed volume, moderate to high density, no definite shape, and flows
- Gas has no fixed volume, low density, no fixed shape, and flows easily
Molecular Model:
a) Structure of states of matter:
- Solids have particles close together, regular pattern, and vibrate on the spot
- Liquids have particles close together, random arrangement, and move around
each other
- Gases have particles far apart, random arrangement, and move quickly in all
directions
b) Relate properties to forces and distance between molecules and motion:
- Solids have fixed volume due to regular pattern and strong attraction, high
density due to close together, definite shape due to same as fixed volume, and
do not flow due to regular pattern
- Liquids have fixed volume due to close molecules, moderate density due to less
close than solids, no definite shape and flowing as they can move past each other
- Gases have no shape due to fixed arrangement, low density due to far apart, no
fixed volume due to moving around, and flow because moving around
c) Interpret temperature of gas in terms of the motion of its molecules:
- High temperature, molecules move faster
d) Describe pressure of gas in terms of motion of molecules:
- High pressure due to faster movement
e) Pressure in terms of change in momentum:
- Faster movement, more particles striking walls of container, greater pressure
f) Random motion of particles in suspension as evidence for kinetic theory:
- Smoke (oil droplets) are seen to move randomly
- Motion is evidence that air particles (invisible) are also moving randomly and
colliding with the smoke droplets
- The air particles cannot be seen but their motion can be understood by the smoke
droplets which can be seen
g) Brownian Motion:
- Random motion in various directions
Evaporation:
iv)
v)
vi)
a) Describe evaporation in terms of the escape of more energetic molecules from the
surface of the liquid:
- All temperatures there is distribution of kinetic energy within liquid
- Molecules with highest kinetic energy can escape and become gas
b) Subsequent cooling:
- Average speed of molecules will decrease when fast ones escape
- Temperature of liquid will decrease
c) Demonstrate understanding of how temperature, surface area, and draught over a
surface influence evaporation:
- Temperature: Increases evaporation as more particles have sufficient energy to
escape
- Draught: Increases evaporation as moving air carries away water molecules
- Surface area: Increases evaporation as more molecules are close to the surface
d) Explain cooling of object in contact with evaporating liquid:
- Evaporation of liquid takes thermal energy away from object too
Pressure changes:
a) Effect of volume (at constant temperature) and temperature (at constant volume) on
pressure:
- As volume decreases, distance between each collision with the wall decreases,
molecules collide with wall more often, average force against wall will increase,
pressure will increase
- As temperature increases, kinetic energy of molecules increases, speed increase,
strike walls with more force, pressure increase
b) Recall and use equation:
- P1V1 = P2V2
Thermal expansion:
a) Thermal expansion of solids, liquids, and gases and constant pressure:
- Solids and liquids made up of tiny vibrating particles which attract each other
- Higher temperature, faster vibration
- Vibrations take up more space, object expands in all directions
- Gas will collide with container with more force and regularity, if container
dimensions are free to change it will expand
b) Everyday applications of thermal expansion:
- Solid: Railway lines given space to expand at end of line, jam jar lids are heated if
they are not opening, overhead cables given slack to allow for contraction,
thermostat has bimetal strip that bends when heated too much (bends towards
one which expands less)
- Liquid: Thermometers have liquids that expand on heating
- Gases: Car tires pressure will increase as they become hot while driving,
convection currents
c) Difference between solids, liquids, and gases:
- Different levels of freedom, different kinds of expansion
Measurement of Temperature:
a) Physics properties used for measurement:
- Volume: Increases with temperature: used for Mercury in glass thermometer
- Resistance: Increases with temperature: used for Resistance thermometer
- Current: Increases with difference: used for Thermocouple thermometer
- Current: Increases with temperature: used for Thermistor thermometer
b) Recognise the need for and identify fixed points:
- Used to calibrate thermometers
- Boiling and melting water can be used as these 2 changes occur at fixed
temperatures
- The thermometer can be placed in boiling and melting water to make marks
c) Describe structure and action of liquid-in-glass thermometers:
- As temperature rises, liquid expands
- At any temperature liquid will have fixed volume
d) Demonstrate understanding of sensitivity, range, and linearity:
- Sensitive thermometers have threads of liquid that move further for rise in
temperature, sensitivity increased by narrower tube, more expanding liquid
- Range is difference between highest and lowest point on thermometer, increased
by using liquid with greater gap between melting and boiling point
- Linearity: Within range, expansion is uniform
e) Describe structure of thermocouple:
- Consists of two metals
- When one junction between two metal types is higher than other voltage is
produced
- Voltage is dependent on temperature difference between junctions
- They have a large range and can record temperature very quickly
vii)
Thermal capacity:
I.
Relate a rise in temperature to increase in internal energy:
- Internal energy = random kinetic energy + potential energy of particles
- If temperature rises, kinetic energy has increased
- Rise in kinetic energy causes rise in internal energy
II.
Simple molecular account:
- Higher temperature, molecules have more kinetic energy, internal energy
increased
III.
Show an understanding of the term thermal capacity:
- Energy required to raise temperature by 1K
IV.
Use equation:
- Thermal capacity: Change in energy/change in temperature
- Specific heat capacity x mass
V.
Define specific heat capacity:
- Energy required to raise a unit mass of a substance by 1K
VI.
Use equation:
- Change in temperature/ mass x change in temperature
- Energy transferred = Mass x specific heat capacity x change in temperature
VII.
Describe experiment:
- Measure temperature of material before and after heating
- Measure energy input from heating by measuring voltage, current, and time
- Insulate object to avoid losing energy
viii)
Melting and boiling:
I.
Describe as no change in temperature:
- Melting and boiling are changes in state, wherein the energy input does not
reflect in a change in temperature
II.
State meaning of melting and boiling point:
- Melting point: Temperature at which solid and liquid phases exist in equilibrium
- Boiling point: Temperature at which substance changes from a liquid to a gas
throughout the bulk of a liquid
III.
Condensation and solidification:
- Condensation: Kinetic energy of particles falls, attractive forces slowly pulls them
back into droplets, bonds are formed
- Solidification: Kinetic energy of particles decreases, permanent bonds are
formed, no longer able to move freely
IV.
Distinguish between boiling and evaporation:
- Boiling happens only at fixed point, evaporation is at all temperatures
- Boiling happens throughout the liquid, evaporation is only at surface
- Boiling affects all particles, evaporation only the particles with sufficient kinetic
energy
- Boiling keeps same temperature of liquid, evaporation decreases
V.
Latent heat of vaporisation and fusion:
- Vaporisation: Energy change associated with a substance boiling or condensing
- Fusion: Energy change associated with a substance melting or solidifying
- Molecular interpretation: Transition bonds are being broken or formed, this gives
an associated intake or release of energy
VI.
Define specific latent heat:
- Amount of energy per mass unit absorbed or released during a change of phase
VII.
Describe experiment:
- Take volume of liquid to its boiling point
- Measure mass
- Boil water for fixed period and calculate energy input through voltage, current,
and time
- Record mass of liquid after heating and calculate mass turned into gas
- L = Current x time x voltage / Mass 1 – Mass 2
- Heat ice until it starts to melt
- Capture melted ice in the beaker on the balance
- Heat for fixed length of time and calculate energy input by measuring the voltage
and current supplied by heater
- Measure mass of water melted during that period
- L = Current x time x voltage / Mass of Water melted
VIII.
Equation:
- Energy transferred = mass x specific latent heat
ix)
Conduction:
x)
xi)
a) Describe experiments to demonstrate properties of good or bad conductors of heat:
- Wax and coin are attached to object to be tested
- Other end of object heated
- Ability of object to conduct heat can be judged by how quickly wax melts and
coins are released
- Rods coated with thin layer of wax can be connected to boiling tank
- Length of melted wax shows which material is best conductor
b) Give a simple molecular account of heat transfer in solids:
- When a material is heated, particles move faster, push on neighboring particles,
and speed up those too
- All materials conduct like this, but metals have free electrons in lattice which
speed up when heated and collide with atoms to speed them up
- Thermal energy is rapidly transferred to all parts
c) Insulation examples:
- Plastic foam lagging around hot water tank to prevent heat loss
- Glass or mineral wool insulation in loft to keep house cool
- Wall cavity filled with plastic foam, beads, or mineral wool
- Double glazed windows with two sheets of air between them
Convection:
a) Recognise convection as important method of thermal transfer in fluids
b) Relate convection to density changes and describe experiments:
- Hot water expands and becomes less dense, rises upwards and cooler, denser
water sinks and displaces it
- Where water is heated, its particles gain energy and vibrate more rapidly
- As particles circulate, they transfer energy to other parts of beaker
- Heat water with potassium permanganate crystals to colour
c) Convection examples:
- Beaches, land heats up more quickly than sea, warm air rises above land, is
displaced by cooler air from sea, night sea stays warmer, land cools down quickly,
warmer air rises above sea, is displaced by cooler air moving out from land
- Hot water system has cold water in storage tank which sinks down to boiler, is
heated, heated water rises to top and collects in storage tank which is insulated
- Room heating has heater at bottom to create convection current
- Fridge has freezer at the top
Radiation:
a) Identify infra-red radiation as part of electromagnetic spectrum:
- Sun’s energy travels in form of invisible infrared waves as well as light
- Can travel through a vacuum
- Heat up things that absorb them
b) Recognise that thermal energy by radiation does not require medium:
- Infrared and light rays are electromagnetic
- Do not need medium to propagate
c) Describe the effect of surface colour and texture on emission, absorption, and
reflection of radiation:
xii)
- Emitters: Black best to white worst, dull best to shiny worst
- Reflectors: Black worst to white best, dull worst to shiny best
- Absorbers: Black best to white worst, dull best to shiny worst
d) Describe experiments to show properties of emitters and absorbers:
- Emitters: Metal cube with matt black and shiny white faces filled with boiling
water, thermal radiation detector placed at same distance from both, meter
readings compared
- Absorbers: Matt black and shiny white plates placed at same distance from
radiant heater, thermometer placed behind both to measure rises in temperature
e) Amount of radiation emitted depends on surface temperature and surface area of
body:
- Greater surface temperature, greater emission
- Greater surface area, greater emission
f) Vacuum flask:
- Insulated stopper to reduce conduction and convection
- Double-walled container with gap between walls, air removed to reduce
conduction and convection
- Walls have silvery surfaces to reduce thermal radiation and reflect
Consequences of Energy Transfer:
a) Identify application:
- Conduction: Saucepan or wok: Made of copper or other good conductors
- Convection: Air conditioner: Normally placed on ceiling
- Radiation: Paint: Hot climate houses are painted white
3. Properties of Waves:
I.
General Wave Properties:
a) Demonstrate understanding that waves transfer energy without transferring matter:
- Example is swing
- When someone is pushed, the mass of pusher stays where it is
- Kinetic energy just has to be transferred
b) Wave motion in ropes and springs and experiments using water waves:
- Particles in rope vibrate in fixed positon and energy in particles are transferred
from one end of rope to other end
- Wave travels as a “sideway pulse”
- Water waves ensure that an object that is floating experiences and up and down
motion
- Waves carry energy without the net movement of particles
c) Use the term wavefront:
- Lines connecting points with the same phrase on propagation
d) Meaning of speed, frequency, wavelength and amplitude:
- Amplitude: A: Maximum displacement from mean position (meter)
- Frequency: f: The number of oscillations that take place in 1 second (Hertz)
- Wavelength: Shortest distance between two points in phase with one
another (meter)
-
II.
Wave speed: v: The speed at which wave fronts pass a stationary observer
(relative to speed of light)
e) Recall and use equation:
- Velocity (m/s) = frequency (Hz) v wavelength (m)
f) Distinguish between two types of wave and give examples:
- Transverse: Oscillation is perpendicular to direction of energy propagation:
seismic S waves, all electromagnetic waves
- Longitudinal: Oscillation is perpendicular to direction of energy transfer: Seismic
P waves, sound waves: form compressions and rarefactions (bunched up and
stretched out)
g) Describe how waves can undergo:
- Reflection at plane surface: Waves are reflected from surface at same angle as
they strike it (presuming surface is smooth)
- Refraction: If a surface allows waves to pass through, the speed of wave change
due to different density. As frequency is unchanged, a decrease in speed causes
a decrease in wavelength, and wavefronts gap changing causes change in
direction of travel
- Diffraction: Waves bend round side of obstacle or spread out as they pass
through a gap
h) Effect of wavelength and gap on diffraction:
- Diffraction only significant if the size of the gap is about the same as the
wavelength
- Wider gaps produce less diffraction
i) How wavelength affects diffraction at an edge:
- Long wavelength causes greater diffraction in waves
- This is why television waves are more difficult to receive in hilly areas than radio
waves which have a longer wavelength and why the diffraction of light is so
difficult to observe
j) Use of water waves to observe processes:
- Put water in tank and use motor to produce vibrations
- Place vibrating block to produce ripples
- Vertical surfaces put in path for reflection
- Flat piece of plastic makes water more shallow and slows wave for refraction
- Obstacle being placed shows ripple bending around it for diffraction
Reflection of Light:
a) Describe formation and characteristics of optical image by plane mirror:
- After reflection, some rays enter eye
- These rays appear to come from position behind mirror where image is seen
- Image is: virtual, upright, same size, laterally inverted, same distance as mirror
from object
b) Image is virtual:
- Rays do not actually meet behind mirror
- Therefore image is not real
c) Recall and use law:
III.
IV.
a)
b)
c)
d)
- Angle of incidence = angle of reflection
d) Perform simple constructions, measurements, and calculations:
Refraction of Light:
a) Experimental demonstration:
- Put stick in water
- Stick appears closer to surface of water
- Virtual image
b) Use terminology to describe passage of light:
- Light enters medium with higher density
- Lights slows down and changes path
- Light ray then emerges parallel to original direction (provided object has parallel
sides)
- Refraction will occur if glass were replaced with another transparent material
c) Give the meaning of critical angle:
- The angle of incidence beyond which light will totally internally reflect
d) Describe internal and total internal reflection:
- Less than critical angle, ray splits into a refracted ray and weaker reflected ray
- At critical angle, refracted only just leaves the surface
- Beyond critical angle, ray is totally internally reflected perfectly
e) Use definition of refractive index n in terms of speed:
- Refractive index is measure of the change in speed, carried out by comparing it
to the speed of light
- Medium with highest refractive index slows light down the most, and has the
greatest bending effect
f) Use equation:
- n = sin i/sin r
g) Use equation 2:
- n = 1/sin c
- This is because angle of incidence = 90 (1) if drawing reversed
e) Use of optical fibres:
- Thin, strands of glass that can carry digital signals in the form of pulses of light
- At transmitting end, electrical signals are encoded into light signals by LED
- Photodiode turns them back into electrical signals
- Used to carry long-distance transmission in telephone networks
- Used in high speed communications, such as television and broadband
- Endoscopes used in body to give doctors clear image of inside
Thin converging lens:
Describe action:
- Thin converging lens bend beam of light and form images
Principle focus and focal length:
- The point where rays parallel to principal axis meet is called principal focus
- Distance between centre of lens and principal focus is focal length
Ray diagrams
Ray diagrams
e) Use of single lens as magnifying glass:
- As object is moved towards lens, image becomes bigger and further away
- If it is between lens and F, rays do not meet and image appears to come from
behind lens
- Virtual image formed, cannot be picked up, works like magnifying glass
f) Describe image:
- Enlarged/same size/diminished
- Upright/inverted
g) Understanding of real and virtual image:
- Real image has rays that actually meet and can be picked up on a screen
- Virtual image doesn’t have rays that meet and cannot be picked up
V.
Dispersion of light:
a) Qualitative account of splitting of light:
- Sides of prism are not parallel, so light comes out in different direction
(deviated)
- White light passed through prism splits into a range of colours called a spectrum
- Effect is called dispersion
- Occurs because different colours are each refracted by different account
- Greatest wavelength refracted the least
- Therefore, order: ROYGBIV
b) Light of single frequency is monochromatic
VI.
Electromagnetic Spectrum:
a) Main features of electromagnetic spectrum in order of wavelength:
- Highest frequency and lowest wavelength to lowest frequency and highest
wavelength: Gamma rays, X-Rays, UV, VIBGYOR, Infrared, Radio waves
(Microwaves-UHF-VHF-short wave-medium wave-long wave)
- Rudolph is really underutilizing xylophone gifts
b) Speed of electromagnetic wave in vacuum:
- 3 x 10^8
c) All waves travel at same high speed in vacuum
d) Describe typical properties and uses of radiation:
- Radio and TV communications (Radio waves): Radio waves are used to transmit
TV pictures, will bend around hills due to high wavelength
- Satellite television and telephones (microwaves): Used by mobile phones, for
beaming TV and telephone signals, produce heating effect when absorbed
- Electrical appliances, remote controllers, and intruder alarms (infrared): Security
alarms switched by motion sensors that pick up changing pattern of infrared, all
objects emit some infrared because of motion of their atoms or molecules,
hotter objects emit more infrared
- Medicine and security (X-Rays): X-rays given off when fast-moving electrons lose
energy very quickly, long-wave rays are not very penetrating, can be used to
take photographs that reveal flaws inside metals or body, but damage living
cells deep inside body
e) Describe awareness of safety issues regarding the use of microwaves and X-rays:
-
Microwaves cause internal heating of body tissues, which is dangerous
X-rays can damage living cells deep inside body, and can cause cancer or
mutations
VII.
Sound:
a) Production of sound by vibrating sources:
- Vibrating objects cause compression and rarefactions in the air around them,
which travel to our ears through solids, liquids, and gases
b) Describe longitudinal nature of sound waves:
- Air oscillates backwards and forwards as compressions and rarefactions pass
through it
- Compression passes, air pressure rises
- Rarefaction passes, air pressure falls
- Distance from compression to compression is wavelength
c) Describe compression and rarefaction:
- Compression is area where particles are bunched up
- Rarefaction is area where particles are stretched-out
d) State human range:
- 20 Hz-20,000 Hz
e) Ultrasound:
- Sounds above range of human hearing
f) Medium: S
- Sound waves are mechanical
- Medium is needed for transmission
g) Describe experiment to show speed of sound:
- Known distance from wall, time for echo to return
h) Typical values of speed of sound:
- Gases: 330 m/s in dry air at 0, 350 m/s in dry air at 30 degrees
- Water (pure): 1400 m/s
- Concrete: 5000 m/s
i) Relate loudness and pitch to amplitude and frequency:
- Amplitude: Higher amplitude- greater displacement- greater volume
- Frequency: Higher frequency- more oscillations- higher pitch
j) Reflection of sound causes echo:
4. Electricity and magnetism:
I.
Simple phenomena of magnetism:
a) Describe forces between magnets and between magnets and magnetic materials:
- Magnetic forces seem to come from poles at the end of the magnet
- Two poles: North seeking pole (North Pole) and South seeking pole (South Pole)
- Like poles repel and unlike poles attract
- Magnetic materials are attracted to magnets
b) Magnetic forces causes:
-
c)
d)
e)
f)
g)
h)
i)
j)
II.
a)
b)
Magnetic forces between two bodies exist due to interaction between magnetic
fields
- Electrons have slight magnetic effect when the spin and orbit nucleus
- In magnetic material, atomic
Induced magnetism:
- Magnetic materials are attracted to magnets because they become magnetized
in the presence of a magnet
- The magnet induces magnetism in them, with the pole nearest to the magnet
induced opposite to the pole at the end of the magnet
- Attraction between unlike poles holds material to magnet
Magnetic and non-magnetic materials:
- Magnetic: Can be magnetized and is attracted to magnets (Iron, nickel, cobalt)
- Non-magnetic: Cannot be magnetized and is not attracted to magnets (Brass,
copper, zinc, tin, aluminium, non-metals)
Describe methods of magnetization:
- Stroking: Magnet is stroked across material
- Use of DC in coil: Put in a coil of wire and high DC is passed through wire
- Hammering in magnetic field: Material placed in magnetic field and hammered
Describe methods of de-magnetization:
- Heating: All magnets have temperature at which they lose their magnetism
- Use of AC in coil: Object is magnetized in opposite direction each time current
reverses, but amount of magnetism is reduced each time
- Hammering: Throws atomic magnets out of line
Draw pattern of magnetic field lines around bar magnet:
- Lines heading from N to S of magnet in circular form
- Size of circles increases as you move closer to edge
Describe experiment to find pattern of magnetic field lines including direction:
- Compass held near one end of magnet
- Needle position is marked using two dots
- Compass moved so that needle lines up with previous dot and so on
- When dots are joined, magnetic field lines is formed
- Magnetic field is strongest where lines are closest together
- Compass will point towards S pole
Distinguish between properties of soft iron and steel:
- Soft iron: Soft magnetic material: magnetism is temporary
- Steel: Hard magnetic material: magnetism is permanent
Distinguish between design and use of permanent magnets and electromagnets:
- Permanent: Hard magnetic material: For application when magnetism is needed
over longer periods (fridge doors)
- Electromagnets: Use a solenoid to create magnetic field: For application where
magnetic field needs to be turned on and off: Relay, circuit breakers, storage
Electric Charge:
State that there are positive and negative charges
State that like charges repel and unlike charges attract
c) State that charges are measured in coulombs
d) Describe simple experiments to show production and detection of electric charge:
- Perspex rod rubbed with cloth (positive) will attract polythene rod rubbed with
cloth (negative)
- Charged rode will induce opposite charges in sphere which can then be earthed
- Golf leaf electroscope: If charged object is placed near cap- Charges are induced
in electroscope- other charges are repelled down to leaf- gold leaf diverges
e) State that the direction of an electric field at a point is the direction of the force on a positive
charge at that point
f) Describe an electric field:
- A region in which an electric charge feels a force
g) State that charging a body requires removal or addition of electrons
h) Describe simple field patterns:
- Point charge: Away from positive, towards negative
- Charged conducting sphere: Charges collect at edge as they repel each other,
away from positive and towards negative, strongest at sharpest curve
- Parallel plates: Straight lines from positive to negative, slight curves towards
edge
i) Give an account of charging by induction:
- If charged object is held above uncharged object, charges opposite to charged
object collect near it
- One side of object has more electrons than normal, one has fewer
- If one side is earthed, overall object ends up with charge
j) Distinguish between conductors and insulators and give examples:
- Conductors: Materials that let electrons pass through them, electrons are
loosely held to their atoms, good thermal conductors as well (metals)
- Insulators: Hardly conduct at all, electrons tightly held to atom, can be
transferred by rubbing, easy to charge as electrons that get transferred tend to
stay where they are (non-metals except graphite)
h) Use electron model to distinguish between conductors and insulators:
- In conductor, charges are free to move between atoms
- In insulator, charges are not free to move between atoms
III.
Current:
a) State that current is related to flow of charge
b) Show understanding that current is a rate of flow of charge and use formula (Current =
Charge/Time)
c) Use and describe use of ammeter:
- Measures the current flowing in amperes (A)
- Always placed in series to component of which current is being measured
d) State that current in metal is due to flow of electrons
e) Distinguish between electron flow and conventional current:
- Conventional current direction is taken from + to – around the circuit
- Electrons flow from – to + due to force of repulsion
- CCD defined before electron was discovered
-
IV.
a)
b)
V.
a)
b)
c)
VI.
a)
b)
c)
d)
e)
VII.
Mathematically, transfer of positive charge is same as transfer of negative
charge in opposite direction
Electromotive Force:
State the EMF is electrical source of energy measured in volts
Understand EMF definition:
- Defined in terms of energy supplied by a source in driving charge around a
complete circuit
- EMF: Total energy difference per unit charge around a circuit
- Is the voltage (potential) that a battery will supply
- Is the work done per unit of charge by the cell in driving charge around the
complete circuit
Potential Difference:
State the potential difference across a circuit component is measured in volts
- Measure of how many joules per coulomb (volts) there are in a specific point of
a circuit
- Potential energy represents how much energy is there to drive a current
through the wire and is measured in volts
- Potential difference is the difference in potential between two pints of a circuit
- PD across a component is the work done per unit of charge in driving charge
through the component
Recall that `1V = 1 J/C
Use and describe of a voltmeter:
- Voltmeter measures potential difference across a component
- Always connected in parallel to component
Resistance:
State that resistance = PD / current and understand qualitatively how changes in PD or
resistance affect current:
- If material obeys Ohm’s Law, current will increase in proportion to potential
difference increase (at constant resistance)
- If material obeys Ohm’s Law, current will be inversely proportionate to current
(at constant voltage)
Recall and use equation R = V/I
Describe experiment to determine resistance using voltmeter and an ammeter:
- Voltmeter in parallel, ammeter in series
Sketch and explain the current-voltage in:
- Ohmic resistor: Straight line passing through 0, 0
- Filament lamp: Curved because as current increases, heats up and resistance
increases and current stops increasing proportionately
Effect of length and cross-sectional area on resistance:
- Increasing length = increasing resistance
- Increasing cross-sectional area = decreasing resistance
- R = (pL/A)
- R x A / L = R1 x A2 / L2
Electrical energy:
a) Understand energy transfer:
- Circuits transfer energy from battery/power source into components
- Some is also radiated out to surroundings
b) Recall and use equations:
- Power (W) = Voltage x Current
- Energy (J) = Power (VI) x Time
VIII.
Diagrams:
a) Draw and interpret circuit diagrams containing sources, switches, resistors (fixed and variable),
heaters, thermistors, light-dependent resistors, lamps, ammeters, voltmeters, galvanometers,
magnetising coils, transformers, bells, fuses and relays (skill based)
b) Draw and interpret diagrams containing diodes
IX.
Series and parallel circuits:
a) Understand that current at every point in series circuit is same
b) Calculate the combined EMF of several sources in series
- Add up EMF of each source
c) Give the combined resistance of two or more resistors in series
- Add up resistance of each component
d) Recall and use fact that adding up PDs of each component is equal to PD across supply
e) State that for parallel circuit, current from source is larger than current from each branch
f) Recall and use fact that current from source is equal to sum of currents from each branch in a
parallel circuit
g) Calculate effective resistance of two or more resistors in parallel
- 1/R(total) = 1/R1 + 1/R2
h) State the advantage of connecting lamps in parallel:
- Circuit does not stop working if one goes off
- Can be turned on and off individually
- Each bulb glows brightly
X.
Action and use of circuit components:
a) Variable potential divider (potentiometer):
- Resistor or series of resistors used to vary output voltage
- Changing the position of potentiometer varies voltage
- Voltage dropped across that section of the resistor will vary
b) Describe the action of a diode and show understanding of its use as a rectifier:
- Diode allows current only to flow in one direction only
- Four diodes used to convert AC current to DC
c) Describe the action of thermistors and light dependent resistors and show understanding of
their use as input transducers:
- Transducers: Devices that convert one type of energy into another
- Thermistor: Higher temperature, lower resistance, higher PD across fixed
resistor (in series) and higher current (in parallel)
- LDR: Increasing light intensity, lower resistance, higher PD across fixed resistor
(in series) and higher current (in parallel)
d) Recognise and show understanding of light-sensitive switches and temperature-operated
alarms:
-
LDR’s can be used in light-sensitive switches coupled with relay
Increase of temperature causes current to flow, activating electromagnetic
switch that operates alarm
e) Relay:
-
XI.
a)
b)
c)
d)
XII.
a)
b)
c)
Electromagnetic switch, activated when current is passed through it
When current pulls one switch contact towards or away from each other, can be
used to turn on second circuits
Dangers of Electricity:
State the hazards of:
- Damaged insulation: Risk of electrocution when handling wires
- Overheating of cables: Insulation will melt and wires become exposed
- Damp conditions: Impure water conducts electricity so risk of electrocution
State that a fuse protects a circuit
Explain the use of fuses and circuit breakers and choose appropriate fuse ratings and circuitbreaker settings:
- Fuse: Thin piece of wire which melts and breaks if too much current passes
through it- used to cut circuit if current is too high
- Circuit breaker: Automatic electrical switch which will cut a circuit if the current
is too high- electromagnet arranged to pull bolt away and release switch,
turning off circuit
- Should be set just above optimal current
- Most common ratings 3A, 5A, 13A
Explain the benefits of earthing metal cases:
- Safety wire that connects metal body of the kettle to earth and stops it
becoming live- if something goes wrong inside the appliance and the live wire
touches the metal case, it could cause harm when touched- but earth wire
creates safe route for current to move away- has low resistance, and therefore
breaks fuse
Electromagnetic induction:
Show understanding that a conductor moving across a magnetic field or a changing magnetic
field linking with a conductor can induce an EMF in the conductor:
- When conductor cuts magnetic field (wire or magnetic could be moving),
EMF/current is induced in the wire
- If wire forms part of complete circuit, EMF makes current flow
Direction of induced EMF (and so current) oppose the change causing it:
- Makes magnetic field opposite to field of the magnet
- If N Pole of magnet moved towards solenoid, solenoid will have N pole to repel
it
Factors affecting magnitude of Induced EMF:
- EMF induced in conductor is proportional to rate at which magnetic field lines
are cut by the conductor
- Moving wire faster
- Using a stronger magnet
- Increasing length of wire in magnetic field
d) Reversing direction of induced EMF:
- Moving wire in opposite direction
- Turning magnets around to reverse field
e) State and use relative directions of force, field, and current:
- Hold fingers of right hand parallel to each other
- Thumb is force (direction of motion), first finger is field, second finger gives
current
f) State experiment to demonstrate electromagnetic induction:
- Connect solenoid to galvanometer with centre-zero
- Move magnet towards solenoid
- Check for deflection
XIII.
AC Generator:
a) Distinguish between DC and AC:
- DC: Electric charge only flows in one direction
- AC: Electric charge changes direction periodically
b) Describe and explain rotating coil generator and use of slip rings:
- AC generator used to provide current
- Coil placed in magnetic field and rotated by turning shaft
- Slip rings fixed to coil and rotate with it
- Brushes are two contacts made of carbon which rub against slip rings and keep
coil connected to the outside part of the circuit
- When coil is rotated, cuts magnetic field, so EMF is generated
- Increase EMF by: Increasing number of turns on the coil, increasing area of the
coil, using stronger magnet, rotating coil faster
c) Sketch graph of voltage output against time
d) Relate the position of coil to voltage output:
- When normal to coil is perpendicular to field lines, output is maximum
- When normal is parallel, output is zero
- Therefore when coil is horizontal, output is maximum
- When coil is vertical, output is zero
XIV.
Transformer:
a) Describe construction of basic iron-cored transformer as used for voltage transformations:
- Primary coil placed next to AC input voltage, secondary coil next to output
- Connected with core made of soft magnet (iron or Mumetal)
b) Describe principal of operation for transformer:
- When alternating current flows through input coil, sets up an alternating
magnetic field in the core and therefore in the output coil
- This changing field induces an alternating voltage in the output coil
c) Recall and use equation:
- V2/V1 = n2/n1 (n=Number of coils)
d) Recall and use equation:
- V1I1 = V2I2 (for 100% efficiency, no power lost)
e) Understand terms step-up and step-down:
- Step up: Output coils and voltage higher
- Step down: Input coils and voltage higher
f) Describe use of transformers in high voltage transmission of electricity:
- Output of a power station is high current
- Transformer converts to low current and high voltage before passing through
overhead cables
- Second transformer use to lower voltage before the supply enters homes
g) Advantage of high voltage-transmission:
- Energy lost = I2R
- High current = Higher power loss
- Low current = lower power loss
- Thinner, lighter, and cheaper cables can be used due to low current as well
XV.
Magnetic effect of current:
a) Describe pattern of magnetic field due to currents in straight wires and in solenoids:
- Wire: Hold wire in right hand with thumb in direction of current, fingers give
you magnetic field direction pointing to S pole
- Solenoid: Hold solenoid in right hand with fingers curling in direction of current,
thumb gives direction of magnetic field
b) State the qualitative variation of strength of magnetic field over salient parts of pattern:
- When field lines are closer together, field is stronger
- Direction of arrow shows where compass would point (N to S)
c) Describe applications of magnetic effect, including relay:
- Circuit breakers: Current flows through two contacts, as well as electromagnetwhen current gets too high, electromagnet pulls strongly enough to break the
contact and release the iron catch- contacts open and current stops
- Magnetic relay: Switch operated by electromagnet- small switch with thin wires
can be used to turn on current in much more powerful circuit- current in
electromagnet causes iron armature to be pulled towards it- contact closescurrent flows through larger circuit
d) State that the direction of the magnetic field line at any point is the direction of the force on the
N pole of the magnet at that point
e) Describe the effect on the magnetic field of changing magnitude and direction of current:
- Current reverses: field reverses
- Current increases: strength of field reverses
XVI.
Force on current carrying conductor:
a) Describe an experiment to show that a force acts on a current-carrying conductor in a magnetic
field:
- Place wire in magnetic field and turn on power, wire moves a tiny bit
- If current is reversed, direction of force will be reversed
- If magnetic field is reversed, direction of force will be reversed
b) State relative directions of force, field, and current:
- Hold fingers of left hand perpendicular to each other
- First finger in direction of field
- Second in direction of current
- Thumb gives direction of force
c) Describe an experiment to show the corresponding force on beams of charged particles:
- Electron is opposite to current, so effect will be opposite to left hand rule
- Proton will be in same direction as current
XVII. DC Motor:
a) State that a current-carrying coil in a magnetic field experiences a turning effect and that the
effect is increased by:
- Increasing the number of turns on the coil
- Increasing the current
- Increasing the strength of the magnetic field
b) Relate this to the action of an electric motor:
- Current is passed through a coil
- Experiences a force
- Coil feels a force which rotates the coil
- Commutator is attached to motor to ensure that current direction reverses
periodically
- Without commutator, coil would turn back in previous direction
- Carbon brushes used to keep a constant flow of electricity
5. Atomic Physics:
I.
Atomic Model:
a) Describe structure of atom:
- Nucleus consists of protons and neutrons- net charge positive
- Held in nucleus by nuclear force
- Electrons orbit nucleus at high speed
- Electrons carry negative charge, held in orbit by force of attraction from protons
- Net charge zero as number is equal
b) Describe how the scattering of α-particles by thin metal foils provides evidence for the nuclear
atom:
- Metal foil placed in path of beam of alpha particles from source
- Some passed straight through gold atoms, some were repelled so strongly that
they bounced back or were deflected through large angles
- Therefore atom is mostly empty space and mass in concentrated in centre
(nucleus)
II.
Nucleus:
a) Describe composition of nucleus:
- Protons and neutrons
- Called nucleons
b) State charges:
- Protons: +1
- Neutrons: 0
c) Use term proton number:
- Number of protons in atom
d) Use term nucleon number:
e)
f)
g)
h)
III.
a)
b)
IV.
a)
b)
c)
- Number of protons and neutrons = mass
State meaning of nuclear fission and fusion:
- Fission: Reaction where heavy nucleus splits spontaneously or due to impact
with another particle to release energy
- Fusion: Nuclei with low atomic number fuse to form heavier nucleus, with
release of energy
Use the term nuclide and use notation AZX
- Nuclide: An atom characterized by distinct number of neutrons and protons
Balance equations involving nuclide notation:
Use and explain term isotope:
- Isotopes are atoms of same element with different number of neutrons
- Physical properties vary, chemical are the same
Detection of radioactivity:
Background radiation:
- Small amount of radiation around at all times due to radioactive materials in
environment
- Comes from natural sources such as rocks, soil, air, or even foods and building
materials
- Radon gas is problem when it collects in house
Detecting radiation:
- Window at end is thin enough for particles to pass through
- Radiations enters tube, ionizes argon gas
- This sets up high voltage spark across gas and causes pulse of current in circuit
- Current is amplified and detected on counter
- Tube can be connected to: Ratemeter, Scaler, Amplifier/Loudspeaker
- Reading must be made first without particles to eliminate background radiation
Characteristics of types of emissions:
Discuss random nature of emissions:
- Radioactive emission occurs randomly over space and time
- Cannot predict which nucleus will decay and when
Identify alpha, beta, and gamma by:
- Nature: Alpha (Helium Nuclei, 2 P + 2 N), Beta (1e-), Gamma (electromagnetic
ways similar to X-rays)
- Mass: Alpha high, beta low, gamma no mass
- Speed: Alpha (up to 0.1 x SOL), Beta (up to 0.9 x SOL), Gamma (SOL)
- Ionising power: Alpha (Strong), Beta (Weak), Gamma (Very weak)
- Penetrating effect: Alpha (Not very penetrating, stopped by thick sheet of paper
of few centimetres of air), Beta (Stopped by few metres of aluminium), Gamma
(Very penetrating, never completely stopped, intensity can be reduced by lead
or thick concrete wall)
Describe deflection:
- Alpha: Deflected towards negative parallel to electric field, deflected slightly
perpendicular to magnetic field according to left-hand rule
-
Beta: Deflected towards positive parallel to field, deflected heavily
perpendicular to field with opposite of left hand rule
- Gamma: Not deflected in either field
d) Give examples of practical use:
- Tracers in medicine: Gamma emitter drunk, detector measures activity of tracer
to see how quickly it becomes concentrated (Iodine 123)
- Tracers in industry: Leaks can be detected by adding tracer to fluid
- Sterilisation of food and surgical instruments: Exposure to high dose of gamma
rays can kill al microbes so food is kept fresher and instruments are clean
- Carbon dating: Amount of Carbon-14 remaining says how old object is
- Thickness control
- Radiotherapy: Killing cancer cells with high doses of gamma rays
- Energy generation
V.
Radioactive Decay:
a) State meaning of decay:
- Emission of alpha or beta particles alters number of protons or neutrons
-
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