Electricity Review

Part A

1. If I have 15 C of electric charge going through an ebonite rod, how many electrons are
there in the rod?

2. If I had 35 electrons that were moved into a piece of paper, what would be the charge of
those 35 electrons?

3. You use three charged objects – A, B & C for an experiment on charges. During the lab
you make the following observations

TEST OBSERVATIONS
Bring object A near object B Objects attract each other
Bring object A near object C Objects repel each other
What would happen if object B & C were brought together?

4. If a 2.0 A of current flows through a lightbulb for 20 minutes

a. How many coulombs of charge (Q) have flowed thru the bulb?
b. How many electrons have moved through the lamp?
5. During a lab exam, you are asked to build a circuit with a resistance of 8.00 ohms & a
current intensity of 2.00A. You then insert a voltmeter to measure the potential difference.
a. What will be the reading on the voltmeter? (16.0 V)
b. How much Energy does it require to run for 10 minutes? (19,200 J)
c. If this circuit was running for 20 seconds, what was the charge and how many
electrons went through the circuit? (40 C; 2.5x1020 electrons)

6. Calculate the voltage of a battery that provides 20 joules of energy to every 5 coulombs
of charge. (4V)

7. A device is on for 2 hours & 30 min & consumes 1, 800, 000 J of energy. What is the
amount of wattage used by this device? (200 W)
8. An electrical appliance requires 600. W of power & a current intensity of 4.00 amps. What
is the voltage required for this appliance? (150. V)

9. You accidentally leave your bedroom lights on & go off to school. You know the lights
use 120 volts & have a current intensity of 5.5 amps. You are gone for 5 hours. How much
energy – in Joules and kWh - did the lights use? (11,880,000 J, 3.3 kWh)

10. A 120 V source is connected to a 1500 W Kettle. Find:

a. The current (12.5 A)
b. The Resistance (9.60 Ω)
c. The energy in joules and kWhr for 24 hours in one month. (36.0 kWh)
d. If electricity costs 5.20 cents per kWh, how much would it cost to run the kettle
for one day? ($1.87)
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Problem Solving

1. For the circuit below, what is the terminal voltage of the battery?

2. Consider the circuit in the diagram below

a. What is the total resistance of the circuit?
b. What is the current and power through the 100 ohm resistor?
3. What is the potential difference (voltage) across the 6 ohm resistor?
4. In the circuit below, resistor R1 dissipates 0.40 W. Resistors R2 and R3 are identical.
A. What is the voltage of R2 and R3?
B. What is the resistance of R2? (Challenge/Higher Thinking Question)
5. A circuit has 120 V power supply, and three resistors. Two are parallel that are 30 W and 60 Wrespectively.
The third is just after the power supply and has 20 W. If this circuit is on for 2 hours, how much energy is
required to run this circuit?

20 W

60 W 30 W