Parallel Circuits

11. If one of the resistors in a parallel circuit is removed, the total resistance

  1. decreases
  2. increases
  3. remains the same
  4. doubles

Correct answer: (B)
increases

12. If there are a total of 120 mA into a parallel circuit consisting of three branches, and two of the branch currents are 40 mA and 10 mA, the third branch current is

  1. 50 mA
  2. 70 mA
  3. 120 mA
  4. 40 mA

Correct answer: (B)
70 mA

13. In a certain three-branch parallel circuit, R1 has 12 mA through it, R2 has 15 mA through it, and R3 has 25 mA through it. After measuring a total of 27 mA, you can say that

  1. R3 is open
  2. R1 is open
  3. R2 is open
  4. the circuit is operating properly

Correct answer: (A)
R3 is open

14. In a five-branch parallel circuit, there are 12 mA of current in each branch. If one of the branches opens, the current in each of the other four branches is

  1. 48 mA
  2. 12 mA
  3. 0
  4. 3 mA

Correct answer: (B)
12 mA

15. Six resistors are in parallel. The two lowest-value resistors are both 1.2 kΩ. The total resistance

  1. is less than 6 kΩ
  2. is greater than 1.2 kΩ
  3. is less than 1.2 kΩ
  4. is less than 600 Ω

Correct answer: (D)
is less than 600 Ω

16. The currents into a junction flow along two paths. One current is 4 A and the other is 3 A. The total current out of the junction is

  1. 1 A
  2. 7 A
  3. unknown
  4. the larger of the two

Correct answer: (B)
7 A

17. The following currents are measured in the same direction in a three-branch parallel circuit: 200 mA, 340 mA, and 700 mA. The value of the current into the junction of these branches is

  1. 200 mA
  2. 540 mA
  3. 1.24 A
  4. 900 mA

Correct answer: (C)
1.24 A

18. The following resistors are in parallel across a voltage source: 220Ω , 470Ω , and 560Ω . The resistor with the least current is

  1. 220 Ω
  2. 470 Ω
  3. 560 Ω
  4. impossible to determine without knowing the voltage

Correct answer: (C)
560 Ω

19. The power dissipation in each of four parallel branches is 1.2 W. The total power dissipation is

  1. 1.2 W
  2. 4.8 W
  3. 0.3 W
  4. 12 W

Correct answer: (B)
4.8 W

20. The total resistance of a parallel circuit is 50 Ω. If the total current is 120 mA, the current through the 270 Ω that makes up part of the parallel circuit is approximately

  1. 22 mA
  2. 120 mA
  3. 220 mA
  4. 50 mA

Correct answer: (A)
22 mA

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