Download Name: Date:______ Hour:______ Assignment #______ Power and

Name:_______________________ Date:_________
Hour:______ Assignment #_______
Power and Energy Calculations
Use the following formulas below to solve.
P = IV
P = power in watts (W)
I = current in amps (A)
V = voltage in volts (V)
(Note that if power is in watts, it can be converted to kilowatts by dividing watts by 1000)
1. How much power flows through a circuit with 1 amp and 120 volts?
2. How much power flows through a circuit with 5 amps and 120 volts?
3. How much power flows through a circuit with 10 amps and 120 volts?
4. How much power flows through a circuit with 10 amp and 10 volts?
5. How many volts are needed for a circuit to generate a current of 10 amps and a power of 200 watts?
6. How many volts are needed for a circuit to generate a current of 35 amps and a power of 450 watts?
7. How many amps are required for a 2000W blow dryer operating on 110 volts?
8. How many amps are required for 100W light bulb operate on 110 volts?
E = Pt
E = electrical energy in kilowatt-hours (kW-hrs)
9. How many kilowatthours are used by a 3 kW fire in 5 hours?
10. How many kilowatthours are used by a 7 kW water heater in 2 hours?
11. How many kilowatthours are used by a 2 kW kettle in 1.5 hours?
12. How long does it take a 2 kW fire to use 1kW-h?
13. How long does it take a 6 kW shower to use 1kW-h?
t = time
1. Your oven has a power rating of 5000 watts.
a. How many kilowatts is this? ________________
b. If the oven is used for 2 hours to bake cookies, how many kilowatt-hours (kWh) are used?
Use E = Pt
2. Calculate the power rating of a home appliance (in kilowatts) that uses 8 amps of current when
plugged into a 120-volt outlet. Use P = IV
3. Calculate the power of a motor that draws a current of 2 A when connected to a 12 volt battery.
(P=IV)
4. Your alarm clock is connected to a 120 volt circuit and draws 0.5 A of current.
a. Calculate the power of the alarm clock in watts. (P=IV)
b. What is the power in kilowatts?_____________
5. Using the formula for power, calculate the amount of current through a 75-watt light bulb that is
connected to a 120-volt circuit in your home. (rearrange P=IV to solve for current)
6. The following questions refer to the diagram.
a. What is the total voltage of the circuit? ____________
b. What is the current in the circuit? (Use I = V/R)
c. What is the power of the light bulb? (Use P = IV)
7. A toaster is plugged into a 120-volt household circuit. It draws 5 amps of current.
a. What is the resistance of the toaster? (rearrange I = V/R to solve for resistance)
b. What is the power of the toaster in watts? (Use P = IV)
c. What is the power in kilowatts? ________________
8. A clothes dryer in a home has a power of 4.5 kilo-watts and runs on a special 220-volt household
circuit.
a. What is the current through the dryer? (rearrange P=IV to solve for current)
b. What is the resistance of the dryer? (rearrange I = V/R to solve for resistance)
c. How many kilowatt-hours of electricity are used by the dryer if it is used for 4 hours in one week?
(Use E = Pt)