20.3 Electric Circuits
Transcript 20.3 Electric Circuits
electric circuit is a complete path
through which charge can flow.
Symbols are used to represent parts of a
Source of electrical energy
Devices that are run by the electrical energy
are places where the circuit can be
If the switch is open, the circuit is not a
complete loop, current stops
When the switch is closed, the circuit will
of current is the direction in which
positive charges flow
has only one path it can flow.
If one element stops functioning in a series
circuit, none of the elements can operate.
What are sources of resistance?
electrical circuit with two or more paths
through which charges can flow
is the rate of doing work
Electric power is the rate at which electrical
energy is converted to another form of
Unit is watt (W)
P(watts) = I (amps) x V (volts)
A clothes dryer uses about 27 amps of
current from a 240-volt line. How much
power does it use?
P = I x V = (240V)(27A) = 6500 W
camcorder has a power rating of 2.3 watts.
If the output voltage from its battery is 7.2
volts, what current does it use?
I = P/V = (2.3W)/(7.2V) = 0.32A
power tool uses about 12 amps of current
and has a power rating of 1440 watts. What
voltage does the tool require?
V = P/I = (1440 W)/(12 A) = 120 V
wiring, fuses, circuit breakers,
insulation, and grounded plugs help make
electrical energy safe to use.
All wires must be able to carry max expected
“Blowing a fuse”- a wire will melt if too much
current passes through it
A circuit breaker is a switch that will open when
current is too high
Grounding – the transfer of excess charge
through a conductor to Earth