Power, work and energy

Instructions:

There are 10 questions.

For the multi-choice questions:

  • choose the correct answer
  • write down your answer.

For the calculation questions:

  • calculate the unknown value
  • specify the appropriate unit
  • write down your answer.

Note:

  • You can print this page and write you answers onto it.
  • You can use a calculator.

Use the Ohm's law power triangle and Ohm's law for power in action to assist with the following questions.

1. What is the correct formula to calculate current?

  1. I = P ÷ V.
  2. I = V ÷ P.
  3. I = P x V.

 

2. What is the correct formula to calculate power?

  1. P = I ÷ V.
  2. P = V ÷ I.
  3. P = I x V.

 

3. What is the correct formula to calculate voltage?

  1. V = I ÷ P.
  2. V = P ÷ I.
  3. V = I x V.

 

4. Increasing the circuit current has what effect on the power?

  1. It increases.
  2. It decreases.
  3. It remains the same.

 

5. Increasing the circuit resistance has what effect on the power?

  1. It increases.
  2. It decreases.
  3. It remains the same.

 

6. If the battery voltage is 12V and resistance 4Ω, the power will be 36W. If you double the voltage (eg 24V), what happens to the power?

  1. Halves.
  2. Doubles (2 x).
  3. Quadruples (4 x).

 

7. If the battery voltage is 12V and resistance 4Ω, the power will be 36W. If you halve the voltage (eg 6V), what happens to the power?

  1. Reduces to a quarter.
  2. Reduce by half.
  3. Doubles.
  4. It remains the same.

 

8. Calculate the power in a circuit that has a 36V power supply and a current flow of 2A.

 

9. Calculate the voltage supply in a circuit that has a component with a power rating of 5200W and a current flow of 13A.

 

10. Calculate the current flow in a circuit that has a component with a power rating of 5200W and a supply voltage of 650V.

 

If you had trouble answering the questions about power, get more information from:

  • Electrical principles section in Resources
  • text books
  • internet sites
  • your trainer.

When you have finished:

  • show your answers to your trainer
  • close this window and choose a new activity from the menu.