&
What is Motion?
Relative change in position
↳ What is needed?
>
-
Reference point
·
·
B
A
Point of origin
Two physical quantities
L
Distance
-
Shortest part between two points (is a straight line)
Displacement
Case 2
Case 1
-----------------
↳
N
50 m
50 m
L
↓
Distance = 100 m
Displacement = 0
Distance covered
Distance = 50 m
Displacement = 50 m
-
>
-
4
3
I
-
↓
1
Case 1: shortest distance
Displacement
-
Displacement: vector quantity
Distance: scalar quantity
Types of Motion
5 sec
2 cases
- 5m
↳
5 sec
5m
5 sec
6 sec
↑
5m
5 sec
l
A
5m
5m
↑
3 sec
>
Equal distance covered in equal
intervals: Uniform Motion
>
-
5m
Equal distance in unequal intervals:
Non-uniform motion
W
~
Wind speed is decreasing after increasing: Retardation
> Called as speed
Rate of change of motion -
↓
Time involved
>
- m/km
Speed = Distance
Time
↳ s/hr
↑
- Represented
S.I Unit: m/s >
Km/hr
>
-
↳x 5
m/sec
When motion is nonuniform
Average speed = Total distance
Total time
18
m/s
>
Km/hr
x 18
5
>
-
Avg. speed = 16m + 16m
4+2
= 32 = 16 m/s
6
3
Speed + Direction = Velocity
Velocity = Displacement
Time
Unit: m/s
Scalar quantity
Vector quantity
Only represents numerical value
Numerical value + Direction
Distance
Displacement
Speed
Velocity
Time
Avg. speed = 180 = 3 m/s
60
Avg. velocity = 0 = 0 m/s
60
Rate of change in velocity
Is called Acceleration
5 m/s
5 m/s
5 m/s
Velocity changing with
direction
Change in velocity = Final speed - Initial speed
Acceleration = m/s = m/s
s
a
Case 1
Initial speed = 0
Final speed = 6 m/s
30 s
a = 6 - 0 = 1 = 0.2 m/s
30 5
Case 2
Initial speed = 6 m/s
5s
Final speed = 4 m/s
a = 4 - 6 = -2 = -0.4 m/s
5
5
Graph Representation
Slope = speed
Slope = Acceleration
Velocity
Distance
Time
Time
Area = Motion
Area = Displacement
Numerical of Motion in straight line: The ‘UTSAV’ Concept
3 equations of motions
1 v = u + at
u = initial velocity
Horizontal motion
2 s = ut + 1 at
t = time
2
s = distance
3 v - u = 2 as
a = acceleration
v = final velocity
Straight line motion
Rectilinear motion
Vertical
Horizontal
(a = -g)
Vertical motion
Against the gravity
a=g
Acceleration due to gravity
Free fall
u=0
v = u + gt
h = ut + 1 gt
2
v - u = 2gh
v = u - gt
h = ut - 1 gt
2
v - u = -2gh
Initial speed
Final point = 0
Final velocity = 0
u=0
v = 72 km/hr
5 min
5 x 60 = 300 s
72 x 5 = 20 m/s
18
a = 20-0 = 20 = 1 m/s
300 300 15
s = ut + 1 at
2
s = 0 + 1 x 1 x (300)
2 15
= 3000 m
s = 3 km
u = 18 km/h x 5
18
= 5 m/s
v = 36 x 5 = 10 m/s
18
a = 10-5 = 5 = 1 m/s
5 5
s = ut + at
= 5 (5) + 1 x (5)
2
= 37.5 m
Uniform Circular Motion
Uniform = speed
motion of a body moving with speed along the circular path
a =v
r
Centripetal acceleration
Acceleration towards the
centre in circular path
Change in velocity at every point
A
Displacement = 0
100 m
10 s = 100 m
1 min = 60 sec
B
One Liners (MCQs)
Distance in a particular direction is called velocity
Displacement = velocity
Time
What causes Motion?
↓ Motion is caused due to force
State
↓
Rest
-
-
I
↑
↑
-
L
Motion
Force can:
Bring a rested body to Motion
Bring a moving body to rest
Speed up a body (acceleration)
Speed down a body (applying brakes)
Change the direction of a body
Change the shape/size
Jo
Concept of forces
H S.I unit of force: Newton
Case 1
Represented as “N”
Force is producing the change
in velocity
Case 2
-
10 N
10 N
E
>
Net force = 0
↓
Balanced force
Acceleration = 0
>
-
F
Frictional force
30 N
E
>
Fnet = 30-20
= 10 N
↓
-
10 N
Unbalanced force
>
-
a= 0 No change in velocity
Contact and Non-contact forces
Types of forces
Force
Conservative force
Work done is independent of the
path
Work done is 0 in case of closed
path
Eg: gravitational force, non-contact
force, spring force
Exception
Non-conservative force
Work done is dependent on path
taken
Eg: frictional force
Laws of motion
By Newton and Galileo
However three laws of motion given by Newton
1st Law of Motion
Inertia
Rest
Motion
Direction
Depends on mass
of the object
An object if at rest remains at rest
or if in motion remains in motion at
a constant velocity unless an
external force is applied on it
Current state
Change
Inertia
Resist
Inertia Mass
Examples:
The dry leaves and fruits falls when we shake a tree
A person sitting in a moving car may be pushed forward when the car
stops abruptly as our legs are in contact with the surface
2nd Law of Motion
Momentum
Quantifies motion
p=mxV
M
V
S.I unit of p = Kg m/s
Truck (where mass of the body is more than the velocity)
Bullet bike (where the velocity is more than the mass of the truck)
Derivation
Force = rate of change in momentum
change in momentum = mV - mu
Rate of change in momentum = mV - mu
t
F = vector quantity
F=mxa
m = scalar quantity
= m (V - u)
F = Kg m/s
a = vector quantity
t
Force (f) = ma
p = vector quantity
a
m = scalar quantity
V = vector quantity
F=mxa
F=mx v-u
t
F=5x 7-3
2
5 x 4 = 10 N
2
10 = 5 x v - 3
5
10 = v - 3
V = 13 m/s
3rd Law of Motion
It states that for every action there is an equal and opposite reaction
X
Works on conservation
of momentum and
Newton’s 3rd law
·
↓d Gas expelled out
Conservation of Momentum
↓
Change in velocity not mass
> Conservation principle
Momentum is conserved -
m u + m u = (M + M ) x V
40 x 5
0
40 x 5 = (40 + 3) x V
200 = 43 V
V = 4. 65
One liners (MCQs)
The range of weak nuclear force is of the order of 10 m
Friction depends on the smoothness of the surfaces. The force of friction always
opposes the applied forces
The force of the Earth’s gravity on every kilogram is about 10 N
g = 9.8 m/s
10 m/s
Every kg = 1 x 10
= 10 N
‘Action at a distance force’: Gravitational force
Once a satellite has been launched into orbit, the only force governing its motion is the
force of: Force of gravity
S.I unit of Electrostatic force
In 1785, Charles Augustine Coulomb used the calibrate tortion balance to measure the
force between electric charges
Where q = charge
F=
q q
4 E
Constant
The measure of force that can cause an object to rotate about an axis is called: Torque
Universal Law of Gravitation
Electrostatic Force
mI
mI
r
F L M I M2
r
qI
Both are non-contact
↓
- and conservative
L
forces
(
I
FL
W
-
F = G M MI
r2
If
I
-
Gravitational Constant
Work done is
independent of path
Work done in a close
path is zero
I
-
2
S.I unit
T
Value: 6.67 x 10 Nm/Kg
Discovered by: Henry Cavendish
(1798)
>
-
F=
I
o
-
G = Gravitational constant
I
q 12
q
r
F= 1
q q
4 ↑E 2
r
I
I
q2
r
q = charge
S.I unit of charge: Coulomb
GM M
r
I
I
-
2
N = G Kg
m
I
-
2
>
-
G = Nm
Kg
I
2
Kepler’s Planetary Laws
/
if
A
Ellipse
E
K
T
r
First Law: Law of Orbit
Planets move in elliptical orbits with the Sun as a focus
Second law: Law of Area
The line joining the planet and the Sun sweep out equal areas in equal interval of time
Third law: Law of Time Period
Cube of mean distance of a planet from the Sun is proportional to the square of the time
period/orbital speed
T r
Mercury nearest to Sun: 88 days revolution
Neptune farthest to Sun: 165 yrs revolution
Difference between Mass and Weight
Inertia
Constant
Weight: force by which Earth attracts a mass
Force = m x a
Weight = m x g
Constant
Gravity differs
Variation in gravity
1. Gravity is more in poles than the equator
2. Gravity decreases with altitude
3. Gravity in moon is 1/6th of Earth’s gravity
Vary
g = 9.8 m/s ~ 10 m/s
Different from “G”
which is constant
Thrust: when force is applied perpendicularly
S.I Unit: Newton
Vector quantity
Pressure: scalar quantity
Invented by
Blaise Pascal
1 atm = 10 Pascal
Pressure = Thrust
Area
P = Kgm
s m
= Kg/ms
Unit of pressure
N
m
or N/m
Pressure in Fluids
Buoyant Force
Upward force by liquid
Archimedes Principle
Less buoyant force
River water has less
density No salt content
Same water level
Sea water has high density
High salt content
Ice
High buoyant force
Relative Density
R. D = Density of a substance
Density of water
No unit
Density = Mass
Volume
S.I unit: Kg
m
Work and Energy
What is work?
Force cause a displacement
S.I unit: Nm/Joule
Work = Force x Displacement
Work = FS cos 0
1J=1N.1m
1J=2N.1m
2
1J=1N.2m
2
Work
Scalar quantity
+ve: force and displacement have same direction
Parallel
-ve: force and displacement are antiparallel
0
180
Displacement = 0
Angle between force and displacement is 90
Displacement
Force
James Prescott Joule
Work
What is Energy?
Energy: Capacity to do work
S.I unit: Joule
Biggest source of energy: Sun
Forms of Energy
Mass
Kinetic Energy = 1 m x V
2
Velocity
The energy an object has
because of its motion
K. E = 1 mV
2
Relation between K.E and Momentum
K. E = 1 m V
2m
= (mV) = p = K.E
2m 2m
p = K.E
2m
(2p) = K.E = 4 p
2m
2m
The energy stored in
an object due to its
position
Potential Energy
Eg: Gravitational P.E
Concept of dams based on this
P.E
P.E converted to K.E
P.E becomes less and K.E keeps
increasing
Velocity max
K.E
Energy = mgh
Weight = Force = mg
Work done = Energy = F . S
mgh
Scaler
Law of Conservation of Energy
Energy can neither be created, nor be destroyed. It can be converted
from one form to another
Electrical Heat
1. Dynamo: Mechanical energy Electrical energy
2. Generator: Mechanical energy Electrical energy
3. Motor: Electrical energy Mechanical energy
4. Microphone: Sound energy Electrical Energy
5. Loudspeaker: Electrical energy Sound energy
Rate of doing work
Power = Work
Time
J
S
J/S
Watt
Scalar quantity
Rate of change of velocity = acceleration = V
t
Rate of change of momentum =
p
t
Horse Power
1 HP = 746W
1 HP = 0.746 kW
Power = Force x Velocity
1 kW = 1000 W
P = FV
Bulb
Electrical Energy
Light + Heat energy
Bulb filament made of tungsten (W)
One Liners (MCQs)
Galileo Galilei was the 1st to conclude that in vacuum all objects fall with the same
acceleration g and reach ground at same time
An object falling freely from a height x, after fallen to a height x/2, it will possess
Half potential and half kinetic energy
Constant
The mass of an object on the surface of the moon is 60 N, the mass on the surface of
the earth will be 60 N Weight changes not mass
If an apple is taken to the mountain top, then it’s weight is decreased
Battery: Chemical energy
Electrical energy
The lifting of an object up and down the parade of an army, and the free fall of a
heavy object are all examples of: Rectilinear motion
Oscillatory Motion: to and fro Motion
Follows same Path
Periodic motion: follows same path at particular interval
Sound: it is a form of energy
How is sound produced?
By vibrating objects
Example: vocal chords
--
Vibrate > Produced sound
How sound propagates?
b
Medium between
tuning fork and ears
Types of waves
Sound energy travels in the form of energy
Waves
L
Mechanical wave
Medium is required to
propagate
Ex: Sound waves
............
↑
-
↑
/
The particles in the
medium helps the
sound to propagate
-
Non-mechanical wave
No medium is required to
propagate
Ex: Light waves
Particles do not
move
Compression
Particles
together
Density
Pressure
Rarefaction
Particles far
away
Less density
Particles condensed
More density
Resting position is where the
coils are neither compressed
nor rarified
Wavelength
Characteristics of sound waves
Frequency ( ) = 1 Unit: s ; Hertz
Time
Determines pitch of a sound
Girls have high pitch, high shrillness
vibrates quickly
Amplitude: determines Loudness
Vocal cords
Unit: dB (decibel)
Can be defined as the loudness of the amount of
maximum displacement of vibrating particles of the
medium from their mean position when the sound is
produced
Limit: 0-130 dB
(sound above this
is considered as
noise)
Amplitude
Wavelength
Amplitude
Vibrated 1
time
Time
Time
Vibrated 4
times
Wave taking less
time to vibrate
Timber: quality of sound
Note: sound, which is a mixture of several frequencies
Mosquito: frequency Pitch
Lion: amplitude
Loudness
Audible range: 20 Hz-20,000 Hz
Less than this: infrasonic
sound
Ex: rhinoceros
More than this: ultrasonic
sound
Mach no = Speed of any body
Speed of sound in that medium
Subsonic: Mach < 1
Supersonic: >1 ; < 5
Hypersonic: Mach > 5
Transonic: Mach = 1
Speed of sound
Solid > Liquid > Gas
Light = 3x10 m/s
Speed of light is
more than the speed
of the sound
Reflection of Sound
Sounds reflection: Echo
It is a reflection of sound that arrives
at the listener with the delay after
the direct sound
Source
Distinct reflection
Reflect
Distant: 17.2 m
Distinct reflection
Reverberation: repeated reflection of sound
Repeated sound
reflection
Penetrating power is very high
Applications of Ultrasonic sounds
Produced by bats, dolphins
Ultrasound is banned in gender determination
To monitor growth and development of fetus
Used to identify kidney stones and to break kidney stones
To identify the conditions of our internal organs
SONAR: Sound Navigation and Ranging
Device that is used for detecting and locating
objects specially underwater by the means of
sound waves sent out to be reflected by the
objects
One Liners (MCQs)
Loudness of sound is proportional to the Square of the amplitude of the vibration,
producing the sound
Study of production and propagation of sound waves: Acoustics
If an object executes 10 oscillations per second, then its frequency in kilohertz is
equal to: 0.01
10
1000
The approximate speed of sound in distilled water at 25 C (77 F): 1498 m/s
Sound wave cannot travel through a: wooden hollow pipe placed in vacuum
The velocity of sound in air is affected by the change in the: Atmospheric
pressure, moisture, temperature of air
Temp Velocity
V = velocity of sound in moist air
V. = velocity of sound in dry air
V >V
When the temperature increases the frequency of the sound from an organ pipe
Increases
Stationary waves of frequency 3000 Hz are formed in a medium in which the
velocity of sound is 1200 m/s. The distance between a node and the
neighbouring anti node is?
V=n
1200 = 300 x
=4
I
-
-
-
What is light? - It is a form of energy
It has dual nature Particle and as a form of wave
Light is a form of transverse wave
It can travel in vacuum
It can be polarised
>
Reflection of Light
When a ray of light approaches a smooth polish surface, and the light ray
bounces back
...
Laws of Reflection
1. The angle of incidence = The angle of reflection
2. Incident ray, reflected ray and normal ray all lie in the same plane
>
-
-
Normal
-
-
-
Incident ray
E
i
Reflected ray
i= r
r
-
k
-
Horizontal
perpendicular
Reflecting
surface
Types of Mirror
Plane Mirror
Spherical Mirror
Concave Mirror
Convex Mirror
Reflecting surfaces
curved inwards
Concave Mirror
-
=
-
L
Convex Mirror
Reflecting surface is curved
outwards
C = 2F
Concave
Mirror
Convex
Mirror
Types of Image
Real Image
Virtual Image
It can be obtained on
screen
It is inverted
It cannot be obtained on
screen
It is erect
Image Formation
Image formed behind
the mirror
x
Plane Mirror
1. Image distance = Object distance
2. Object size = Image size
3. Erect Virtual
4. Laterally inverted: Left Right
Right Left
x
Image Fromation
of Concave Mirror
Object
1.
Image
Nature
Focus
Real and Inverted, extremely diminished
2.
Beyond C
C and F
Real and Inverted, diminished
3.
At C
At C
Real and inverted, equal
4.
B/W C and F
Beyond C
Real and inverted, enlarged
5.
At F
Real and inverted, highly enlarged
Image Formation of Convex Mirror
y
+ve
-ve
+ve
x
F
Inverted image
Inverted
-ve
-y
Numericals
Sign convention
u: object distance
-ve (always)
v: image distance
Concave: -ve
f: focal length
Convex: +ve
R: radii of curvature
Mirror Formula
1+1=1
v u f
R = 2F
Height of image
Magnification = h = v
h u
Height of object
Given:
u = -25 cm
f = -15 cm
1+1=1
v u f
1 + -1 = - 1
v 25
15
1=1-1
v 25 15
1=3-5
v
75
1 = -2
v 75
-75 = -37.5 cm
2
h
= -37.5
4 cm -25
37.5 x 4
25
h = -6 cm
Enlarged image
Inverted
Uses of Mirror
Concave
Magnifying
Shaving mirror
Torchlight
Dentist mirror
Convex
Diminishing
Rear view mirror in vehicle
Security reasons In ATMs
Sunglasses
Reflection in street light
Used in solar furnace
Refraction of Light
Types of Medium
1. Rare Medium
2. Denser Medium
Air: rarer
Water
Glass: denser
Medium with more
Density
Case A
When a ray of light travels, its
path changes
1
Rare
2
Denser
No difference
Light ray path is rectilinear
Case B
i
r
Bend towards the
normal
i> r
Case C
i
Denser
Rarer
r
Bend away from
the normal
i< r
Laws of Refraction
1. Incident ray, refracted, ray and normal ray all lie in same plane
2. sin i = constant Given pair of media and light of particular wavelength
sin r
Two mediums
Refraction through a Glass Slab
Rarer
Denser
Lateral Distance
No refraction if strikes
at 90
i= e
Angle of incidence = angle of emergence
Refractive Index
Represented with “n” or “u”
n = Speed of light in air/vacuum
Speed of light in given medium
n
=V
V
Speed of light in air/vacuum: 3 x 10 m/s
Densest medium
Spherical Lens
Lens is transparent
Forms image through refraction
Centre bulged
Ends narrow
Centre narrow
Ends wider
Converging lens
Diverging lens
Image Formation
= Concave Mirror
= Convex Mirror
Image Formation in Convex Lens
Same as Concave Mirror
Beyond C (same)
Image Formation of Concave Lens
Uses
Concave Lens
In treatment of Myopia
Same as Convex Mirror
Convex Lens
In treatment of Hypermetropia
Used as magnifying lens
In camera lens
f = -15 cm
u=?
v = -10 cm
Lens formula = 1 - 1 = 1
v u f
Magnification formula = h = v
h u
1=1-1
u v f
1=1 - 1
u -10 -15
1=1 - 1
u 15 10
1 = 2 - 3 = -1
u
30
30
m = -10
-30
m=1
3
m = 1 object size = image size (same size)
m < 1 h > h (Diminished)
m > 1 h < h (Enlarged)
1
u
u= -30
Power of Lens
Power =
1
Focal Length
+ve
-ve
Convex
Concave
1=m
m
Dioptre (S.I unit of power of lens)
Diffraction: it is bending of light around the corner of an obstacle
Question
Convex lens = 5cm
Concave lens = 10 cm
Convex lens = 2 cm
-10
When all the focal length is
added what power do we
get?
Sol: 5 - 10 + 2 = -3
Concave lens
Control lensT
D
(
Connected to brain
(brain sees the
object not the eye)
L
Aqueous humour
Pupil
L
Eye: Click images/formation
Cornea
Outermost part
Causes refraction of light
Used in eye donation
!
/
Aqueous humour
Provides nourishment to cornea
Maintains eye pressure
Iris
Dark muscular structure
Controls the size of pupil
It also determines colour of the eye
Pupil
To control the amount of light entering the eye
Lens
focuses the light ray on the retina
:
Retina
It is the spot where image is formed
Here optical energy is converted to electrical energy
Blind Spot
Optic nerves meet retina
No image is formed here
Power of Accommodation
Eye can change focal length (situation based)
Ciliary muscles
Least distance of distance of distinct vision: 25 cm
-
Defects of Eye
Myopia/Near Sightedness
Far object not visible clearly
Correction: -ve power lens Concave lens
>
-
Focal length decreases
and Power increases
Image is formed in
front of the retina
Hypermetropia/Far Sightedness
Image formed behind the retina
Light focuses behind the retina
instead of focusing on the retina
Correction: +ve lens Convex lens
Usually occurs above 40 yrs
..
!
:
-
↑
Cannot see nearby objects
Presbyopia
Lens hardens with age Loses flexibility
Age: 55+
Correction: Concave + Convex lens
(Bifocal lens)
Glaucoma/Trachoma
Both caused due to increase in eye
pressure
Glaucoma is hereditary
Not curable
Trachoma is bacterial infection
>
-
Tonometry: to measure your eye pressure
Concave lens
Colour Blindness
It is hereditary
Retina made of cone cells and rod cells
IIIIIIIIIII
Not present in colourblind
people
-
Convex lens
Refraction of Light by a PRISM
V -
·
R
Angle of Deviation
Hi
L
-VX
Wavelength
I'll
D
↓
7
↓
Wavelength↑ Deviation↓
Ray of light away from the normal
Dispersion of White Light in a Glass Prism
-
Consist of 7 different colours
-
Highest wavelength
Less deviation
↑
Decreasing
wavelength
V
↓
More deviation
Red: more speed
Less refractive index
Violet: less speed More refractive index
>
-
>
n = Speed of light in air
Speed of light in prism
Electromagnetic Spectrum
TRICK
Rich
Man
Radio
waves
Micro
waves
in
Victor
Infrared Visible
Uses
X
Gold
UV rays X-ray Gamma rays
Left to right Wavelength decreases and
frequency increases and energy increases
SI unit: Hertz
E = hf
E = hc
wavelength
Due to dispersion
2 refraction and 1 reflection
Rainbow is formed to the
opposite direction of the Sun
Dispersion of white light
here
Refraction in Atmosphere
Twinkling of Stars Due to affects of the Earth’s atmosphere (atmospheric refraction of
star light)
Refractive index
of different types of
gases
In refraction, the actual
position of stars
changes to apparent
position
Advance Sunrise and Delayed Sunset
In this phenomenon, the sun appears to rise early by two minutes
and set late by two minutes. When the rays from the sun hit
atmosphere, they get refracted
Scattering of Light
Blue colour of sky: blue light is scattered more than the other colours because it travels as
shorter, smaller waves
Our sky appears black without atmosphere
Red colour of Sun during sunrise and sunset: red light scatter the least by the molecules
present in the air, so at sunset and sunrise, the sunlight travels longer path through the
atmosphere to reach our eyes. The blue light catches the most and has been mostly
removed, leaving the red light remaining which reaches our eyes.
More wavelength
Tyndall Effect
Colloidal solution scatter the light
>
- most because the dispersed
particles of colloid are bigger and
they defect light
2
1
Why are danger signs red?
>
Red has maximum wavelength and
is least scattered allowing it to
travel long distances without
getting scattered
Total Internal Reflection
Condition of TIR
This phenomenon is responsible for optical illusions
↳ 1. Light should travel from denser to
Examples: Mirage, optical fibers
rare medium
2. light should hit an angle greater
than critical angle
/
-
↓
The layer above the ground
gets warmed. The light ray gets
refracted when light moves
Total internal reflection
through the cold air and into
the hot air layer
>
-
Optical Fibers
ONE LINERS (MCQs)
The materials through which things can be seen are called transparent materials
The reflection on the bathroom mirror, the lake and the glare on pair of glasses are
caused by specular reflection
Gold and copper happen to absorb blue and violet light, leaving the yellow light
The phenomenon which deals with scattering of light by molecules of a medium when
they are excited to vibrational energy levels is called Raman Effect
The phenomena in which mountain tops acquired a rose or orange hue around the
sunrise and sunset is called Alpenglow
Canada balsam has refractive index closes to that of crown glass
↑
↑
What is Electric Current?
Flow of charge per unit time
Flow of electrons per unit time
Electric Current
19
↳
1 e = 1.6 x 10 Coulomb
↳ S.I unit of charge
-
q=nxe
Id
1 C = n x 1.6 x 10
n = 6 x 10 e
is
4)
i=q
t
q=ixt
-
-
I
↑
Electric current is measured by Ammeter
Current S.I unit: Ampere
Charge
L
↑
↑
W
-ve
+ve
-
Current = Charge
Time
Like charges repel each other
Opposite charges attracts each other
-
Conductor: is a material that
conducts electricity/allows electron
to flow through it
Potential Difference
The amount of work done in moving a unit positive charge from one point to other in an
↓
electric field
Measured though: Voltmeter
V=W
· S.I unit: Volt
Potential <
q
difference
↑
Work done to move the
charge
L
1 volt: if one Joule of work is done in moving,
one coulomb of charge
1V = 1J &
1C
Ohm’s Law
By George Simon Ohm in 1827
V
I
V = IR
Resistance
S.I unit Ohm (
The current flowing in a conductor is directly
proportional to the voltage across the conductor,
provided all the physical condition and temperature
remain constant
)
Resistance: the property of a conductor to resist the flow of charge through it
Factors effecting Resistance
1. Length
Length Resistance (More collision of electrons)
2. Area of cross-section
Area Resistance (Less collision of electrons)
3. Temperature
Temperature Resistance
4. Nature of material
Increase movement of e and K.E
Resistivity/Specific resistance
R
R
R
R=
L
1
A
L
A
L
A
= mho/ohm
=lm
m
m
⑳
m=
S.I unit
The resistivity of a material is the
resistance of a wire of that material
Alloy has greater resistivity than its constituent metals
Types of Materials
Conductor: materials that conduct electricity/allow electric flow through them
electrons
Seen in metals
Has free
Semi-conductor: they are materials which have conductivity between conductors and nonconductors or insulator. Eg: Silicon (usually Metalloids)
Insulator: materials that do not allow electricity to pass through them. Eg: Non-metals
such as glass, wood
Resistance of a System of Resistance
Types:
1. Series
2. Parallel
Parallel
Series
R
R
1 =1 +1 +1
R R R R
R
R
R =R +R +R +R
-
-
Series: same current; different potential difference
Parallel: same potential difference; different current
Q. 2 resistors = 20I and 4l (Series)
Connected to a 6 volt battery
Current flow?
>
-
Red = R ↑ + R I
20 + 4 = 24z
6 V = I x 24e
6 =I
1/
/
4 24
0.25 A = I
V = IR
Q. R = 522
; R = 10+ ; R32
= 30
P.d = 12 V
Current?
&
>
-
Parallelly connected
-
V = IR
12 = I x 5
12 = I
5
2.4 A = I
OR
V = IR
12 = I x 10
1.2 A = I
>
-
>
-
V = IR
12 = I x 30
0.4 A = I
2.4 + 1.2 + 0.4 = 4.0 A
1 =1 +1 +1
H
M
Rea R R I R3
1 =1+1 +1
R ed 5 10 30
1=6+3+1
R ec 30
1 = 10
Rea 30
R = 3I
- -
1
- - -
V = IR
/ = I x↓
12
3
I =4A
Heating effect of Electric Current
&
V=W
q
Power = Work Done
Time
Substituting
Electric Power = qV
t
-
-
Electric Power = VI
Heat = Power x t
Heat = VIt
IR x IT
Z
I RT = H
Practical Applications of Heating Effect of Electric Current
:
men
-en
m
↓
Coils in heater made of Nichrome
↓
Alloy of Ni and Cr
m
I
-
Fuse
Low melting point
It is used to protect electrical
appliances from excessive current
and to prevent short circuits or
mismatched loads
-
Filament made of
Tungsten (W)
Has high melting
point
Electric Power
P = VI
P=I R
P=V
R
V = IR
V =I
R
Commercial Unit of Energy
1 unit = 1 kWh
Pxt
1000 x 3600s
36 x 10 Ws
3.6 x 10 J
1 kW = 1000 W
1 unit
1 hr = 60 mins
60 x 60 = 3600 secs
220 V; 50 Hz
In electric appliances
Live wire: Red
Colour of wire
Neutral: Black
Ground/Earth: Green/Yellow
Magnetic Effect of Electric Current
-
~
Discovery
Hans Christian Orsted in 1820
>
>
/
Heating effect of electric
current: James Joule (1840)
Electric current passed through the
wire
d
>
-
V
Causing deflection in the
compass whenever there is
a current in wire showing
current carrying wire
produces a magnetic field
around it
V
Direction of magnetic field changes due
to change in direction of current in the
wire
Magnetic Field Lines
↳
Iron fillings align themselves with
Same poles repel each other
-
- when spread
the magnetic field >
across a magnetic bar, they
respond to magnetic effect of the
bar magnet and align themselves
accordingly
Different poles attract each other
>
>
>
-
Magnetic field lines originate from North Pole
outside the magnet and terminate at South Pole
Magnetic field line are in the form of closed
loop
Magnetic field lines never intersect each other
d
L
Vector quantity
=>
If they insect, there will be
two directions of magnetic
field lines which is not
possible
If magnetic field lines are closer
Field↑
-
Magnetic
Magnetic Field due to a Current Carrying Conductor
Magnetic field lines around a straight
conductor carrying current are concentric
circles whose centre lie on the wire
Magnetic Field
1
Distance
Distance
Current
Maxwells Right Hand Thumb Rule
to find direction of magnetic field
Magnetic Field
Magnetic Field
Direction of current changes
Magnetic Field changes
Direction of
Current upwards: Magnetic field
Current downwards: Magnetic field
Anti-clockwise
Clockwise
South Pole
North Pole
Clockwise
Anti-clockwise
Maxwell’s screw rule to find
direction of magnetic field in a
straight current carrying conductor
Magnetic Field due to a Current carrying Circular Loop
No. of turns in loop
Magnetic Field
Distance
Magnetic Field
Current
Magnetic Field
In centre, the magnetic
field lines are parallel
and uniform
Magnetic Field due to a current carrying Solenoid
Behaves like a bar magnet
when current is passed
In a solenoid the magnetic field is
maximum inside the solenoid
It is uniform
Current passed through a
solenoid
If direction of current is
Magnetic field lines outside the
reversed, the direction of
solenoid is very weak Considered to
magnetic field is also
be practically zero
reversed
Electromagnetic
Soft iron rod that behaves like
a magnet when current is
passed through it
Force on a Current Carrying Conductor in a Magnetic Field
Current direction upwards
Magnetic field
Motor works on principle of Fleming’s Left Hand Rule
Electric energy
Mechanical energy
Force will be
Maximum: the angle between the conductor and the magnetic
field is 90
Minimum: The conductor is placed along the direction of
magnetic field, whether parallel or antiparallel
Zero
Used when a current carrying
conductor is introduced in an
external magnetic field
Electromagnetic Induction
Generator work on this concept
It is the phenomenon in which
electric current is generated by
charging magnetic fields
Discovered by Michael Faraday in
1831
When the bar magnet is pushed
towards the coil, the pointer in the
galvanometer deflects
The relative motion between the
magnet and the coil is responsible
for generation of electric current in
the coil
Generator
Energy
Mechanical Energy
Electrical
Short circuit: it is caused due to breaking of insulation of wires, forming the contact
between live wire and neutral wire
Current in a circuit increases abruptly
One Liners (MCQs)
Device that is used to either break an electric circuit or to complete it: Switch
Gustav Robert Kirchhoff stated that at a junction in electric circuit, the sum of
currents flowing in the junction is equal to the sum of current flowing out of the
junction
Wheatstone Bridge is an arrangement of four resistors used for accurate
measurement of resistance
Coil of wire in an electric room heater is known as: Element
The current in the bulb will stop flowing if the circuit is broken
In the symbol of electric cell, the thicker, shorter line represents the: Negative
terminal
Michael Faraday gave the concept of electric field for the first time
The scientist who was awarded an Noble Prize for the services to Theoretical Physics,
and specially for his discovery of Law of Photoelectric Effect: Albert Einstein
E = hv