1. Chapter 20 Super Review Circuits

3. 1. What is the potential difference across a resistor of 6 Ω that carries a current of 3 A?

4. V = IR V = 3 x 6 V = 18 V

5. 2. A light bulb has a resistance of 36 Ω when operating at 12 V. What is the current?

6. V = IR 12 = I x 36 1/3 A = I

7. 3. If a 60 W light bulb is connected to a 120 V circuit, what is the current?

8. P = IV 60 = I x 120 0.5 A = I

9. 4. A 1000 W heater has a current of 10 A. What is the potential difference?

10. P = IV 1000 = 10 x V 100 V = V

11. 5. Three resistors are 3 Ω, 4 Ω, and 5 Ω. If connected in series, what is the equivalent resistance?

12. R S = R 1 + R 2 + R 3 R S = 3 + 4 + 5 R S = 12 Ω

13. 6. Two resistors, 4 Ω and 8 Ω are connected in parallel. What is the equivalent resistance?

14. 1/R P = 1/R 1 + 1/R 2 1/R P = 1/4 + 1/8 1/R P = 0.25 + 0.125 1/R P = 0.375 R P = 2.67 Ω

15. 7. What is the equivalent resistance of the circuit shown above?

16. R S = R 1 + R 2 R S = 5 + 3 R S = 8 Ω

17. 8. What is the equivalent resistance of the circuit shown above?

18. 1/R P = 1/R 1 + 1/R 2 1/R P = 1/12 + 1/6 1/R P = 0.0833 + 0.167 1/R P = 0.25 R P = 4.0 Ω

19. 9. What is the power output of the circuit shown above?

20. R S = R 1 + R 2 R S = 5 + 3 R S = 8 Ω V = IR12 = I x 8 I = 1.5 A P = IVP = 1.5 x 12 P = 18 W

21. 10. What is the power output of the circuit shown above?

22. 1/R P = 1/12 + 1/6 R P = 4.0 Ω V = IR8 = I x 4.0 I = 2 A P = IV P = 2 x 8 P = 16 W

23. 11. A potential difference of 120 V is placed across a resistor with a current of 0.50 A. What is the resistance of this resistor?

24. V = IR 120 = 0.5 x R 240 Ω = R

25. 12. A 6 Ω resistor has 7 A of current. What is the potential difference?

26. V = IR V = 7 x 6 V = 42 V

27. 13. Three resistors of 5 Ω, 7 Ω, and 9 Ω are connected in series. What is their equivalent resistance?

28. R S = R 1 + R 2 + R 3 R S = 5 + 7 + 9 R S = 21 Ω

29. 14. Two resistors, both 20 Ω, are connected in parallel. What is the equivalent resistance?

30. 1/R P = 1/R 1 + 1/R 2 1/R P = 1/20 + 1/20 1/R P = 2/20 = 1/10 R P = 10 Ω

31. Hint: When two resistors of the same resistance are connected in parallel, the equivalent resistance is ½ of one of the resistances. In the previous example with two 20 Ω resistors, ½ of 20 Ω is 10 Ω. Hint: When two resistors of the same resistance are connected in series, the equivalent resistance is ½ of one of the resistances. In the previous example with two 20 Ω resistors, ½ of 20 is 10 Ω.

33. 1/R P = 1/R 1 + 1/R 2 + 1/R 3 1/R P = 1/3 + 1/4 + 1/5 1/R P = 0.33 + 0.25 + 0.2 1/R P = 0.78 R P = 1.28 Ω