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Unit 10 (Electricity):
Review Problems
1.
The Hollands like to keep their 40.0 W front porch light on at night to welcome visitors. If the light is on from 6 PM
until 7 AM, and the Hollands pay 12.00 cents per kilowatt-hour, how much does it cost to run the light each week? (44
cents)
2.
While cooking dinner, Dean’s oven uses a 220 V line and draws 8.00 A of current when heated to its maximum
temperature. What is the resistance of the oven when it is fully heated? How much power is being dissipated as dinner
cooks? (27.5 , 1760W)
3.
Valerie’s 180 W electric rollers are plugged into a 120 V line in her bedroom. a) What current do the electric rollers
draw? b) What is the resistance of the rollers when they are heated? c) Draw a schematic diagram of the circuit with an
ammeter and voltmeter. (1.5 A, 80 )
4.
Find the equivalent resistance of the circuit. Redraw the circuit with its equivalent resistance. Find the current through
the battery. Using ohm’s law, find the current through and voltage drop across each resistor. (.8A, .8A & 2.4V, .8A &
4V, .8A & 5.6V)
Vs = 12 volts
Device
Current (A) Voltage (V) Power (W)
3
+
Power Supply
12V
5
12V _
Ra = 3
Rb = 5
7
Rc = 7
5.
Find the equivalent resistance of the circuit. Redraw the circuit with its equivalent resistance. Find the current through
the battery. Using ohm’s law, find the current through and voltage drop across each resistor. (6A, 4A & 8V, 1.33A &
8V, 6.67A & 8V)
V = 8 volts
s
+
8V _
2
6
12
Device
Power Supply
Current (A)
Voltage (V)
8V
Power (W)
Ra = 2
Rb = 6
Rc = 12
6.
Find the equivalent resistance of the circuit. Redraw the circuit with its equivalent resistance. Find the current through
the battery. (8, 2.5A)
3
5
20V
+
_
2
1.5
3