𝑰=
𝑸
𝒕
𝑽 = 𝑰𝑹
𝑷 = 𝑰𝑽 =
𝑬
𝒕
I – current (amps) (A)
Q – charge (coulombs) (C)
t – time (seconds) (s)
V – voltage, potential difference (volts) (V)
R – resistance (ohms) (Ω)
P – Power (watt) (W)
E – Energy (joules) (J)
e = 1.6 × 10–19 C
1. The current through a lightbulb is 2.0 amperes.
a. How many coulombs of charge pass through the bulb in 1 minute?
b. How many electrons is this?
2. 10.0 coulombs of charge are transferred through a wire in 5.0 s. What is the current?
3. An iron operates on 120 volts and draws 10 amperes of current. It is left running for 5 mintues.
a. Calculate the charge transferred.
b. Calculate the resistance.
c. Calculate the power.
d. How many joules of energy were used?
4. In a simple circuit, a 110 V electric heater draws 2.0 amperes of current.
a. Calculate the resistance.
b. Calculate the power.
5. A potential drop of 50 volts is measured across a 250 Ω resistor.
a. Calculate the current.
b. Calculate the power.
6. In a flashlight, a battery provides a total of 3.0 volts to the bulb. The lightbulb is operating at a resistance
of 5.0 Ω.
a. Calculate the current.
b. Calculate the power.
c. If the flashlight runs for 3 minutes, calculate the amount of energy used.
7. 4.0 A passes through a 30 Ω resistor.
a. Calculate the voltage.
b. Calculate the power.
8. A 60 watt bulb is running in your home with 120 V.
a. Calculate the resistance in the filament of the bulb.
b. Calculate the current through the bulb.
c. Calculate how many joules of energy it uses in 30 minutes.
9. Find the current through a 12 ohm resistor when 24 volts is applied.
10. Find the resistance of a circuit that draws 0.06 amperes with 12 volts applied.
11. Find the applied voltage of a circuit that draws 0.2 ampere through a 4800 ohm resistor.
12. Find the applied voltage of a telephone circuit that draws 0.017 amperes through a ressitance of 15,000
ohms.
13. A 20 volt relay has a coil with resistance of 200 ohms. How much current does it draw?
14. A circuit has 1200 ohms of total resistance with 12 V. What is the current?
15. A small appliance in your home is rated for 10 amps when connected to 120 volts. What is the power
rating?
16. When connected to 110 V, a blender has 2.7 A of current passing through its motor. What is the power
used by the blender?
17. If a clock uses 2 W of power when running on a 1.5 V battery, what is the current?
18. If you run a 90 W juicer that is being supplied with 4.5 A. What is the resistance?
19. Amanda uses a hair dryer connected to 110 V drawing 11 A of current. What is the power rating of the
dryer?
20. A lamp is rated at 40 W with a resistance of 100 Ω. Calculate the voltage.