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7-2 Electric Current Notes
What is an Electric Current?
The ___________________________ through a wire of conductor is called
___________________________
Current is usually the flow of _____________________
Electric current is measured in __________________ (___)
Charges flow from ___________ voltage to __________ voltage (_______
_______________________-must be present)
 A voltage difference is the ______________ that causes charges to move.
Voltage difference is measured in ______________.
For charges to flow, the wire must always be connected in a ____________
____________________________
If the circuit is broken by removing the battery, or the lightbulb, or one of
the wires, current will ______________________.
Batteries
To keep an electric current continually flowing in the electric circuit a
voltage difference needs to be maintained in the circuit.
A battery can provide the voltage difference that is needed to keep current
flowing in a circuit.
_______________________ as long as there is a __________________
that connects one battery terminal to the other battery terminal.
Dry-Cell Batteries
A cell consists of _____________________ surrounded by a material called
an ____________________.
The electrolyte enables charges to move from one electrode to the other.
One electrode is the carbon rod, and the other is the zinc container.
The electrolyte is a __________________ containing several chemicals.
The cell is called a dry cell because the electrolyte is a moist paste, and not
a liquid solution.
Sources of Electricity
A _________________________ produces a voltage
difference between its _____________ container and
its _______________ suspension rod, causing current to flow between them
Sources of Electricity
A ____________________________ contains two connected plates made
of different ___________________ in a conducting _________________
 A wet-cell battery contains several wet cells connected together.
Sources of Electricity
____________________ have a voltage difference across the __________
_____________ of an electrical outlet, and a generator at a ______________
_________________ provides this voltage difference
What is Resistance?
________________________________
 _________________________ the _____________ of electrons
 electrical energy is converted to _______________________
&__________
 all materials have ____________ electrical resistance
 Resistance is measured in ______________ (____)
 Making wires _________________________, or hotter ____________
the resistance
Ohm’s Law
Ohm’s Law – the current in a circuit equals the voltage difference divided
by the resistance
V: potential difference (V)
I: current (A)
V=I×R
R: resistance ()
 Voltage ________________ when ________________ increases.
 Voltage ________________ when ________________ increases.
Ohm’s Law Problem
 A lightbulb with a resistance of 160  is plugged into a 120-V outlet.
What is the current flowing through the bulb?
Question 1
__________ is the net movement of electric charges in a single direction.
A. An open circuit
B. Electric current
C. Proton flow
D. Voltage
Question 2
What is a volt?
Answer
Question 3
What is the tendency for a material to oppose the flow of electrons called?
Answer
What property of electric current causes light bulbs to give light?
Notes 7-3 Electrical Circuits
Electrical Circuits
Circuits rely on generators at power plants to produce a _____________
__________________ across the outlet, causing the charge to move when
the ______________________
Example
 Hair dryer plugged into wall outlet
 Generator at power plant produces voltage difference
 Dryer and circuit in house contain conducting wires to carry current
 Hair dryer turns electrical energy into thermal energy and mechanical
energy
 Unplug hair dryer opens circuit and breaks path of current
The Current in a Simple Circuit
A simple electric circuit contains a source of ________________________,
such as a battery, a device, such as a lightbulb, that has _________________,
and ____________________ that connect the device to the battery terminals.
When the wires are connected to the battery terminals, ________________
____________________________in the ____________________________.
Circuit Components
A - battery
B - switch
C - light bulb
D - resistor
Types of Circuits
_________________
circuit – the current has only ___________________
to flow through
_________________ circuit – are used in ___________________________
_____________________________________
Series Circuit
current travels in a _________________ path
–_______________________ - one _________
____________ the flow of current
current is the ______________ throughout circuit
–lights are ______________ brightness
each device receives a ________________ of the total voltage
–gets ________________ as lights are added
____________________ – if any part of a series circuit is disconnected, ____________________________________ through the circuit
Example: _______________________

Parallel Circuit
Parallel circuit – contains ______________________________ for current
to move through.
The current can flow through both or either of the branches.
Example: _____________________________
Advantage
When one branch of the circuit is opened, such as when you
turn a light off, the current continues to flow through the
other branches.
Household Circuits
Household circuits mainly use ________________circuits connected
in a logical network.
Electrical energy enters your home at the _________________________or
_________________ and branches out to wall sockets, major appliances, and
lights.
Guards against overheating electric wires:
____________________________ – contains a small piece of metal that
melts if the current becomes too high, opening the circuit and stopping the
flow of current.
To enable current to flow again in the circuit, you must _____________the
blown fuse with a new one.
Too many appliances in use at the _____________________ is the most
likely cause for the overheating of the circuit.
Household Fuse Box
Guards against overheating electric wires:
______________________ – contains a small piece of metal that bends
when it gets hot, opening the circuit and stopping the flow of current.
Circuit breakers usually can be reset by pushing the switch to its “on”
position.
Breaker Box
Electrical Power
Electrical energy is easily converted to mechanical, thermal, or light energy.
Electrical power – the __________________________________________
______________________________________________________________
Electrical Power - rate at which electrical energy is ___________________
to another form of energy
P: _________________ (____)
I: _________________ (____)
V: ________________________ (__)
P=I×V
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Electrical Power is expressed in ________________________
The unit for power is the watt (W). Because the watt is a small unit of
power, electric power is often expressed in ______________________
One kilowatt equals _________________________.
P (watts) = I (amperes) x V (volts)
To calculate the amount of energy an appliance uses:
The unit of electrical energy is the kilowatt-hour, which equals 1000
watts of power used for one hour.
Energy = power x time
E (kWh) = P (kW) x t (h)
Electrical Power
A calculator has a 0.01-A current flowing through it. It operates with a
potential difference of 9 V. How much power does it use?
Electrical Energy
Electric companies charge by the amount of electrical energy used, rather
than by the electric power used.
Electrical energy usually is measured in units of kilowatt hours (kWh) and
can be calculated from this equation:
Electrical
Energy
–energy use of an appliance depends on power required and time used
E: __________________ (__________)
E=P×t
P: __________________ (________)
t: __________________ (_____)
The Cost of Using Electrical Energy
• The cost of using some household appliances is given in this table,
where the cost per kWh is assumed to be $0.09/kWh.
Electrical Energy
A refrigerator is a major user of electrical power. If it uses 700 W and
runs 10 hours each day, how much energy (in kWh) is used in one day?
Question 1
What is an open circuit?
Answer
Question 2
The rate at which electrical energy is converted to another form of energy is
called __________.
A. electrical fuse
B. electrical switching
C. electric power
D. thermal energy
Question 3
Which of the following equations is used to calculate electric power?
A. P = IV
B. P = I/V
C. P = V/I
D. P = AV
Why do homes have a fuse box or circuit breaker?
How does it work?