20 Kirchhoff’s Laws Quiz Questions and Answers

1. What does Kirchhoff’s Current Law (KCL) state?
A. The sum of voltages in a loop is zero.
B. The total current entering a junction equals the total current leaving it.
C. The voltage drop across a resistor is proportional to the current.
D. The current is the same through all components in series.
Answer: B
Explanation: KCL is based on the conservation of charge, meaning that at any junction in a circuit, the incoming current must equal the outgoing current.

2. In a circuit junction, 5 A enters from one wire, 2 A enters from another, and 4 A leaves through one wire. What is the current leaving through the remaining wire?
A. 1 A
B. 3 A
C. 5 A
D. 7 A
Answer: B
Explanation: According to KCL, total incoming current (5 A + 2 A = 7 A) equals total outgoing current. If 4 A leaves through one wire, then 7 A – 4 A = 3 A leaves through the other.

3. For a closed loop in a circuit with a 10 V battery and a 5 V voltage drop across a resistor, what must be the net voltage if another 5 V drop occurs?
A. 0 V
B. 5 V
C. 10 V
D. 15 V
Answer: A
Explanation: Kirchhoff’s Voltage Law states that the sum of all voltages around a closed loop is zero, so 10 V – 5 V – 5 V = 0 V.

4. In a series circuit, if the voltage across the first resistor is 2 V and across the second is 3 V, what is the battery voltage if the loop is closed?
A. 1 V
B. 5 V
C. 6 V
D. 3 V
Answer: B
Explanation: KVL requires that the sum of voltage drops equals the source voltage in a loop, so 2 V + 3 V = 5 V.

5. A junction has currents of 10 A and 15 A entering, and 12 A leaving. What is the current in the fourth branch?
A. 3 A entering
B. 13 A leaving
C. 5 A entering
D. 7 A leaving
Answer: B
Explanation: KCL states that total incoming current (10 A + 15 A = 25 A) equals total outgoing current. If 12 A leaves through one branch, then 25 A – 12 A = 13 A leaves through the fourth branch.

6. In a loop with two batteries (6 V and 4 V) and a 2 V voltage drop, what is the net voltage?
A. 8 V
B. 0 V
C. 10 V
D. -2 V
Answer: B
Explanation: KVL dictates that the algebraic sum of voltages is zero, so 6 V + 4 V – 2 V – (another voltage to balance) = 0 V, assuming the loop is complete.

7. If 8 A flows into a node and 3 A leaves through one path, how much current must leave through the other two paths combined?
A. 5 A
B. 8 A
C. 11 A
D. 3 A
Answer: A
Explanation: By KCL, total outgoing current must equal incoming current, so if 8 A enters and 3 A leaves through one path, the remaining outgoing current is 8 A – 3 A = 5 A.

8. For a circuit loop with a 12 V source and voltage drops of 4 V and 8 V, what does KVL confirm?
A. The drops exceed the source.
B. The net voltage is zero.
C. There is infinite current.
D. The source is insufficient.
Answer: B
Explanation: KVL ensures that 12 V – 4 V – 8 V = 0 V around the loop.

9. At a junction, currents of 2 A, 4 A, and 1 A are leaving. What must be the incoming current?
A. 7 A
B. 3 A
C. 1 A
D. 5 A
Answer: A
Explanation: KCL requires that total incoming current equals total outgoing current, so the incoming current must be 2 A + 4 A + 1 A = 7 A.

10. In a loop with a 9 V battery and two 3 V drops across resistors, what is the voltage at the end of the loop?
A. 9 V
B. 0 V relative to start
C. 3 V
D. 6 V
Answer: B
Explanation: KVL states that returning to the starting point, the total voltage sum is zero, so 9 V – 3 V – 3 V = 3 V, but the loop closes at zero net.

11. If a node has 6 A entering and currents of 2 A and 1 A leaving, what is the current in the third branch?
A. 3 A entering
B. 5 A leaving
C. 3 A leaving
D. 1 A entering
Answer: C
Explanation: KCL: Total outgoing = incoming, so 2 A + 1 A + x = 6 A, thus x = 6 A – 3 A = 3 A leaving.

12. For a circuit with a 15 V source and 5 V and 10 V drops, what does KVL indicate?
A. Overvoltage
B. Balanced loop
C. Short circuit
D. Open circuit
Answer: B
Explanation: 15 V – 5 V – 10 V = 0 V, confirming the loop is balanced as per KVL.

13. At a junction, 10 A enters, 4 A leaves, and 3 A leaves. What is the current in the fourth wire?
A. 3 A entering
B. 7 A entering
C. 3 A leaving
D. 13 A leaving
Answer: A
Explanation: KCL: 10 A incoming = 4 A outgoing + 3 A outgoing + x, so x = 10 A – 7 A = 3 A entering (as it must balance).

14. In a loop with batteries of 10 V and 5 V (opposing), and a 3 V drop, what is the net?
A. 12 V
B. 0 V
C. 2 V
D. -2 V
Answer: B
Explanation: KVL: 10 V – 5 V – 3 V + (adjustment) = 0 V for a closed loop.

15. A junction sees 7 A entering from one wire and 2 A entering from another. If 4 A leaves, what leaves the third?
A. 5 A
B. 3 A
C. 9 A
D. 1 A
Answer: A
Explanation: Total incoming = 7 A + 2 A = 9 A; total outgoing = 4 A + x = 9 A, so x = 5 A.

16. For a loop with 20 V source and drops of 10 V and 10 V, KVL shows:
A. Net gain of 20 V
B. Zero net voltage
C. Loss of 20 V
D. Infinite voltage
Answer: B
Explanation: 20 V – 10 V – 10 V = 0 V, as required by KVL.

17. If 9 A enters a node and 2 A leaves one path, with 3 A leaving another, what is the third path’s current?
A. 4 A leaving
B. 6 A entering
C. 4 A entering
D. 14 A leaving
Answer: C
Explanation: KCL: 9 A incoming = 2 A outgoing + 3 A outgoing + x; x = 9 A – 5 A = 4 A entering (to balance).

18. In a circuit loop, a 7 V battery and 2 V drop with another 5 V drop result in:
A. 14 V total
B. 0 V net
C. 7 V drop
D. 5 V gain
Answer: B
Explanation: KVL ensures 7 V – 2 V – 5 V = 0 V.

19. At a junction, currents of 5 A and 6 A enter, while 8 A leaves. What is the other leaving current?
A. 3 A
B. 1 A
C. 11 A
D. 3 A entering
Answer: A
Explanation: Total incoming = 5 A + 6 A = 11 A; if 8 A leaves, then 11 A – 8 A = 3 A leaves the other path.

20. For a loop with 8 V source and 4 V drop, plus 4 V drop, KVL confirms:
A. 8 V excess
B. Zero sum
C. Negative voltage
D. Open loop
Answer: B
Explanation: 8 V – 4 V – 4 V = 0 V, satisfying KVL.