SAT VOCAB 3
• Attribute (v) to credit, assign (n) a facet or
trait
• Permeate (v) to spread throughout, saturate
• Transmute (v) to change or alter in form
• Reciprocate (v) to give in return
SAT VOCAB 3
Over the Thanksgiving break, many get together for a big
family dinner. Whatever your family tradition is, the recipes
for the different dishes are ___________________ to family
members or friends because each recipe comes from a
different person. My family always has a grits casserole, a
custom that has _________________ now to all the holiday
dinners. Some friends have tried to make the dish, but its
form has _________________ with each person’s attempt to
make it. If we invite friends to our Thanksgiving family
dinner, they ______________________ by bringing a dish
themselves.
ELECTRICITY
ELECTRIC CHARGES
• Atoms are composed of three main parts:
– Proton, p+, positive, located in the nucleus
– Neutron, no, neutral, located in the nucleus
– Electron, e- , negative, located outside the
nucleus in the electron cloud.
• Everything is made of atoms.
ELECTRIC CHARGES
• Protons and electrons have a property called
electric charge.
• An atom has equal numbers of positive and
negative charges so they cancel each other out.
• Electrons can move from one atom to another
atom. This movement is called electric
current.
STATIC ELECTRICITY
• Some atoms hold their charges more
tightly.
• Latin word “stasis” which means
“stays”.
• Static electricity is the temporary
building up of charge on an object.
• Protons DON’T move.
• Only electrons move.
• In static electricity, the charges build
up and stay – they do not flow.
STATIC ELECTRICITY
• When you walk across a carpet, FRICTION
causes electrons to move from the carpet to your
shoe. This is a build-up of static electricity. You
discharge the electricity by touching a
conductor.
LAW OF CONSERVATION
OF CHARGE
• When an object becomes charged, the electric
charge is neither created nor destroyed – it just
came from another object.
• Static electricity is an imbalance in the amounts
of positive and negative charges on the surface of
an object.
STATIC ELECTRICITY
• Another way to generate static electricity is
with a Van de Graaf generator.
• American physicist Robert Jemison Van de
Graaf invented the Van de Graaf generator
in 1931.
• Van de Graaf generator
STATIC ELECTRICITY
• There are three ways to charge on object:
– Friction
– Induction
– Conduction (contact)
STATIC ELECTRICITY
• Charging by Friction
- The charge is
transferred because
of rubbing two
objects together.
- Example: shoes on
a carpet
- Animation
STATIC ELECTRICITY
• Charging by Induction
– Involves the charging of one object by another
object WITHOUT direct contact.
– Example: balloon and rice cereal/electroscope
STATIC ELECTRICITY
• Charging by Conduction
– Involves the DIRECT CONTACT of a charged
object to a neutral object.
– Example: Van de Graaf generator
STATIC DISCHARGE
• Objects do not hold a static charge forever –
objects tend towards equilibrium – they want to
be neutral.
• When electrons move toward this equilibrium –
static discharge occurs.
– Humidity – water (a polar molecule) vapor in the air
pulls electrons off negatively charged objects,
preventing static charges to build up.
– Sparks and Lightning - objects reaching
static equilibrium
CONDUCTORS
• Allow the easy flow of electricity
• loosely bound electrons that are free to move
from atom to atom
• Examples: metals like aluminum, gold, copper
and silver .
INSULATORS
• Insulators – resists the flow of electrons
– hold more tightly to their valence
electrons.
– Examples: plastic, rubber, glass
VOCABULARY
Electric field - the electric force per unit
charge; it is radially outward from a positive
charge and radially in toward a negative point
charge.
ELECTRIC CURRENT
• The constant flow of electrons.
ELECTRIC CURRENT
REMEMBER:
• Conductors let electrons move easily.
• Insulators do not let electrons move easily.
• A SEMICONDUCTOR has conductivity
somewhere between an insulator and a
conductor. Devices made of semiconductors, notably silicon, are essential
components of most electronic circuits.
ELECTRIC CURRENT
There are three parts to an electric charge
- Voltage
- Current
- Resistance
VOLTAGE
• Voltage - For electrons to flow there must be a
potential difference between two places.
• This is called VOLTAGE which is the “push” that
causes electrons to flow.
• It is electrical “pressure”.
• Charges flow from high voltage to low voltage.
• Units: Volts, V
CURRENT
• Current - the measure of how many
electrons per second are flowing through
the wire is the amperage.
• Units: amps
• The number of
electrons
flowing per
second.
current
Electrical current is like the amount
or volume of water flowing through
the hose.
There are two types of current:
AC – alternating current
DC – direct current
RESISTANCE
• Resistance - the tendency for a material to
oppose the flow of electrons.
• Different materials have different amounts
of resistance to the flow of electrons.
• Unit: ohm, R.
RESISTANCE
EXAMPLES:
• gold, silver, and copper have low
resistance, which means that current can
flow easily through these materials.
• Glass, plastics, and wood have very high
resistance, which means that current cannot
pass through these materials easily.
• Resistance
RESISTANCE
• Thin wires provide more resistance than do thick
wires.
• Resistance in wires produces a loss of energy (usually
in the form of heat), so materials with no resistance
produce no energy loss when currents pass through
them.
• Resistance also depends on temperature, usually
increasing as the temperature increases.
•
ELECTRIC CURRENT
OHM’S LAW
• In a material, the current (I) is directly
proportional to the voltage (V) and
inversely proportional to the resistance.
• Ohm’s LAW
OR
OR
ANALOGY
Water in a Hose
DC in a Wire
Electrical Units
pressure
voltage (V)
Volts, V
volume
current (I)
Amps, A
friction
resistance (R)
Ohms, R
Charge, Current, and Voltage review
PRACTICE
What is the current produced with a 9-volt
battery through a resistance of 100 ohms?
I=?
R = 100 ohms
𝑉
I=
𝑅
9 𝑣𝑜𝑙𝑡𝑠
=
100 𝑜ℎ𝑚𝑠
V = 9 volts
= 0.09amps
BATTERIES
TWO TYPES:
1. Dry Cell – the electrolyte is not really dry; but is a paste.
– Standard AA, C, D type batteries, electrolyte is a paste. The “+”
terminal is carbon.
2. Wet Cell – the electrolyte is a liquid (car battery)
– In a car battery, the electrolyte is sulfuric acid.
VOCABULARY
1. Dry Cell – a type of chemical cell, commonly
used today, in the form of batteries, for many
electrical appliances. It uses a paste electrolyte,
with only enough moisture to allow current to
flow.
2. Wet Cell – An electric battery is a device
consisting of two or more electrochemical cells
that convert stored chemical energy into electrical
energy using a liquid electrolyte
BATTERIES
Batteries have three parts.
- A cathode (+)
- An anode (-)
- An electrolyte.
The cathode (positive) and anode
(negative) at either end of a
traditional battery) are hooked up
to an electrical circuit.
BATTERIES
• The chemical reactions in the battery causes a build up
of electrons at the anode.
• This results in an electrical difference between the
anode and the cathode - an unstable build-up of the
electrons.
• The electrons wants to
rearrange themselves to get rid
of this difference. They do this
in a certain way. Electrons
repel each other and try to go to
a place with fewer electrons.
ELECTRICAL CIRCUIT
• They provide a pathway for electrons to
flow.
Four Parts:
1. Energy Source
2. Load
3. Wires
4. Switch
ELECTRICAL CIRCUIT
OPEN CIRCUITS – pathway is broken.
ELECTRICAL CIRCUIT
CLOSED CIRCUITS – pathway is complete.
SERIES CIRCUIT
• Provides only one path for the electrons to follow.
1. A break in the circuit stops the flow of electricity to
all other parts of the circuit.
2. With multiple light bulbs (more resistance) the
current reduces and the lights become dimmer.
3. Ammeters should be wired in series.
SERIES CIRCUIT
RULES
1. The same current flows through
each part of a series circuit.
2. The total resistance of a series
circuit is equal to the sum of
individual resistances.
a. What is the total voltage across the bulbs? 6V
b. What is the total resistance of the circuit? 3Ω
c. What is the current in the circuit? 2A
d. What is the voltage drop across each light
bulb? 2V
e. What happens to the brightness of each bulb
in a series circuit as additional bulbs are added?
Why?
PARALLEL CIRCUIT
• The different parts of the circuit are on separate
branches.
• A break (like a burned out light bulb) in the circuit
does not stop the flow to the remaining devices.
• Multiple light bulbs will remain the same
brightness since the resistance is not decreasing as
it does in a series circuit.
• Each pathway can be separately switched off
without affecting the others.
PARALLEL CIRCUIT
• Household circuits – Wired in parallel, with a
standard of 120 volts.
• Voltmeters are wired in parallel.
HOUSEHOLD CIRCUITS
• Many appliances draw electricity from
the same circuit.
• If the wires get too hot due to too much
electricity, a fuse can blow or circuit
breaker can flip.
• Circuit Breaker – a piece of metal bends
when it gets hot and “flips” the breaker to
the off position.
• Fuse - a piece of metal melts when it gets
hot and causes a break in the circuit.
PARALLEL CIRCUIT
• The more paths the LESS
the resistance.
– Water example again:
added pipes coming from a
large tank will allow more
water to flow out that a
single pipe.
– Therefore as resistance
decreases, current
increases; they are
inversely proportional.
PARALLEL CIRCUIT
RULES
1. Voltage is the same across each component of
the parallel circuit.
2. The sum of the currents through each path is
equal to the total current that flows from the
source.
a. What is the voltage across each
resistor? 12V
b. What is the current in each branch?
6 A and 4 A
c. What is the total current provided by the
battery?
10 A
CIRCUITS
Series and Parallel Review
Question: What is the major difference between a
series circuit and a parallel circuit – in your own
words – put in your notes.
SCHEMATIC DIAGRAMS
• All circuit drawings need at least the following:
– Power supply, wire, resistors, switches, other
items include connectors, meters, etc.
• There is a set of standard symbols used to represent
these items in a diagram of the circuit.
SCHEMATIC DIAGRAMS
SCHEMATIC DIAGRAMS
• Draw a series circuit. Include a power source,
wires, several resistors (light bulbs) and a switch.
SCHEMATIC DIAGRAMS
• Draw a parallel circuit. Include a power source,
wires, several resistors (light bulbs) and a switch.
LIGHT BULB
Electricity flows through the circuit. If the bulb is
broken, so is the circuit.
TRANSPORTING
ELECTRICITY
A transformer is a device that increases of decreases
alternating current generated by a power plant so it can
enter homes safely.
VOCABULARY
Lightning Rod - a metal rod or metallic object
mounted on top of an elevated structure, such as
a building, a ship, or even a tree, electrically
bonded using a wire to interface with the
through an electrode, engineered to protect the
structure in the event of lightning strike.
ELECTRICAL POWER
• The rate at which electrical energy is transferred by an
electric circuit.
• Use Joule’s Law: Power = current x voltage.
• Unit: watt, W
• A kilowatt hour is what the power company uses to
determine how much electricity or energy you used.
• Energy used = Power (kW) x Time (hours).
• E= P x t
• To find cost, you would multiply the energy by the
amount per kilowatt hour.
ELECTRICAL POWER
PRACTICE
1. 105 V are used to power an appliance that needs 15.0
amps. What is the power used?
V = 105V
P=?
I = 15.0amp
P=IxV
P=IxV
= (15.0amp)(105V)
= 1575 W
= 1.575 kW
ELECTRICAL POWER
PRACTICE
2. How much energy is used when this appliance is used
for 30.0 days, 24hrs a day?
E=?
Time = 30 days x 24 hours/day
= 720hr
P = 1.575kW
E = Power x time
E=Pxt
= (1.575kW)(720hr)
= 1134 kW hour
ELECTRICAL POWER
PRACTICE
3. If the power company charges 8¢/Kw-h, what is the
cost of the energy above.
Cost = Energy x price per kW hr
E = 1134kW hour
Cost = ?
Price = $0.08/kW hr
Cost = E x price
= (1134kW hr)($0.08/kW hr)
= $90.72
CIRCUIT PRACTICE
CIRCUIT PRACTICE
2. In this circuit, three resistors receive the same amount of current (4
amps) from a single source. Calculate the amount of voltage "dropped"
by each resistor, as well as the amount of power dissipated by each
resistor. The voltage drop is calculated by multiplying current in the
circuit by the resistance of a particular resistor: V = IR.
1Ω- ____________ 2Ω- ____________ 3Ω- ____________
CIRCUIT PRACTICE
3. Use the series circuit pictured to answer questions a-e.
a. What is the total voltage across the bulbs? ___________
b. What is the total resistance of the circuit? ___________
c. What is the current in the circuit? _________
d. What is the voltage drop across each light bulb?
e. Draw the path of the current on the diagram.
CIRCUIT PRACTICE
4. Use the parallel circuit pictured right to answer questions
a-c.
a. What is the voltage across each resistor? ____
b. What is the current in each branch? ____
c. What is the total current provided by the battery? ______
CIRCUIT PRACTICE
5. Use the parallel circuit to answer questions a-c.
a. What is the voltage across each resistor? ___________
b. What is the current in each branch?______________
c. What is the total current provided by the battery?
_________