# Worksheet: Power and Energy

In this worksheet, we will practice using the formula P = E/t to calculate the rate at which energy is transferred by a device given the amount of energy it transfers in a given time.

**Q2: **

Which of the following is the correct unit for power?

- ASecond
- BVolt
- CJoule
- DAmp
- EWatt

**Q4: **

A kettle is filled with water and turned on. It takes 3 minutes to boil the water, and the kettle is supplied with 324,000 J of energy in this time. What is the power of the kettle?

**Q5: **

A 30 mW LED in an electronic circuit is left on for 2 hours. How much energy does it transfer to its environment over this time? Assume that the LED is efficient.

**Q6: **

How many watts are there in 1 megawatt?

**Q7: **

What is 34 kJ in joules?

**Q8: **

Jennifer wants to find out how much electrical power her television needs when it is on. She watches television for a few hours and records how much energy has been supplied to it every half hour. The graph shows her results.

How much energy has been supplied to the television after 3 hours?

What is the power of her television?

**Q9: **

What is 6,700 kilowatts in megawatts?

**Q10: **

Which of the following is the correct formula for the energy transferred, , in a given time, , for an electrical appliance with a given power, ?

- A
- B
- C
- D
- E

**Q11: **

What is 50 MW in watts?

**Q13: **

What is 24 MW in kilowatts?

**Q14: **

How many joules are there in 1 kilojoule?

**Q15: **

What is 5,000 joules in kilojoules?

**Q17: **

Which of the following is the correct unit for energy?

- AJoule
- BVolt
- CWatt
- DAmpere
- ECoulomb