Circuits & Kirchhoff Laws for Competitive Exam Prep

Circuits & Kirchhoff Laws

Q. What is the effect on the total resistance in a circuit when more resistors are added in series?

A. Increases
B. Decreases
C. Remains the same
D. Becomes zero

Solution

Adding more resistors in series increases the total resistance, as total resistance is the sum of individual resistances.

Correct Answer: A — Increases

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Q. What is the effect on the total resistance when more resistors are added in parallel to a circuit?

A. Increases
B. Decreases
C. Remains the same
D. Doubles

Solution

Adding more resistors in parallel decreases the total resistance of the circuit.

Correct Answer: B — Decreases

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Q. What is the equivalent resistance of a circuit with a 10 ohm and a 5 ohm resistor in series?

A. 15 ohms
B. 5 ohms
C. 10 ohms
D. 20 ohms

Solution

For resistors in series, R_eq = R1 + R2 = 10 ohms + 5 ohms = 15 ohms.

Correct Answer: A — 15 ohms

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Q. What is the equivalent resistance of a circuit with two 10Ω resistors in series and one 5Ω resistor in parallel with them?

A. 5Ω
B. 10Ω
C. 15Ω
D. 20Ω

Solution

R_series = 10Ω + 10Ω = 20Ω. R_parallel = 1/(1/20 + 1/5) = 4Ω. Therefore, R_eq = 4Ω.

Correct Answer: C — 15Ω

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Q. What is the equivalent resistance of a circuit with two resistors R1 = 10Ω and R2 = 10Ω in parallel?

A. 5Ω
B. 10Ω
C. 20Ω
D. 15Ω

Solution

The equivalent resistance in parallel is given by 1/R_total = 1/R1 + 1/R2 = 1/10 + 1/10 = 1/5. Therefore, R_total = 5Ω.

Correct Answer: A — 5Ω

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Q. What is the equivalent resistance of three resistors of 2Ω, 3Ω, and 5Ω connected in parallel?

A. 1Ω
B. 2Ω
C. 0.83Ω
D. 10Ω

Solution

1/Req = 1/R1 + 1/R2 + 1/R3 = 1/2 + 1/3 + 1/5 = 0.8333, thus Req = 1.2Ω.

Correct Answer: C — 0.83Ω

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Q. What is the equivalent resistance of three resistors of 2Ω, 3Ω, and 6Ω connected in parallel?

A. 1Ω
B. 2Ω
C. 3Ω
D. 4Ω

Solution

1/R_eq = 1/R1 + 1/R2 + 1/R3 = 1/2 + 1/3 + 1/6 = 1. Therefore, R_eq = 1Ω.

Correct Answer: A — 1Ω

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Q. What is the equivalent resistance of three resistors of values 2Ω, 3Ω, and 5Ω connected in parallel?

A. 1Ω
B. 2Ω
C. 0.83Ω
D. 10Ω

Solution

1/R_eq = 1/R1 + 1/R2 + 1/R3 = 1/2 + 1/3 + 1/5 = 0.8333, thus R_eq = 1.2Ω.

Correct Answer: C — 0.83Ω

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Q. What is the equivalent resistance of three resistors of values 2Ω, 3Ω, and 6Ω connected in parallel?

A. 1Ω
B. 2Ω
C. 3Ω
D. 4Ω

Solution

1/Req = 1/R1 + 1/R2 + 1/R3 = 1/2 + 1/3 + 1/6 = 1. Therefore, Req = 1Ω.

Correct Answer: B — 2Ω

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Q. What is the equivalent resistance of two resistors of 10 ohms and 20 ohms connected in series?

A. 30 ohms
B. 20 ohms
C. 10 ohms
D. 5 ohms

Solution

In series, the equivalent resistance R_eq = R1 + R2 = 10 ohms + 20 ohms = 30 ohms.

Correct Answer: A — 30 ohms

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Q. What is the equivalent resistance of two resistors of 4Ω and 12Ω connected in parallel?

A. 3Ω
B. 4Ω
C. 6Ω
D. 8Ω

Solution

Using the formula for parallel resistors, 1/R_eq = 1/R1 + 1/R2 = 1/4 + 1/12 = 1/3. Therefore, R_eq = 3Ω.

Correct Answer: C — 6Ω

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Q. What is the equivalent resistance of two resistors of 5 ohms and 10 ohms connected in parallel?

A. 3.33 ohms
B. 15 ohms
C. 5 ohms
D. 7.5 ohms

Solution

Using the formula for resistors in parallel, 1/R_eq = 1/R1 + 1/R2, we find R_eq = 1 / (1/5 + 1/10) = 3.33 ohms.

Correct Answer: A — 3.33 ohms

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Q. What is the equivalent resistance of two resistors of 5Ω and 10Ω connected in parallel?

A. 3.33Ω
B. 5Ω
C. 7.5Ω
D. 15Ω

Solution

1/Req = 1/R1 + 1/R2 = 1/5 + 1/10 = 2/10 + 1/10 = 3/10. Therefore, Req = 10/3 = 3.33Ω.

Correct Answer: A — 3.33Ω

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Q. What is the potential difference across a 10Ω resistor if a current of 2A flows through it?

A. 5V
B. 10V
C. 20V
D. 15V

Solution

Using Ohm's Law, V = I * R = 2A * 10Ω = 20V.

Correct Answer: C — 20V

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Q. What is the potential difference across a 10Ω resistor if a current of 4A flows through it?

A. 20V
B. 40V
C. 10V
D. 30V

Solution

Using Ohm's Law, V = I * R = 4A * 10Ω = 40V.

Correct Answer: A — 20V

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Q. What is the power dissipated in a 10Ω resistor carrying a current of 2A?

A. 20W
B. 30W
C. 40W
D. 50W

Solution

Power P = I^2 * R = (2A)^2 * 10Ω = 4 * 10 = 40W.

Correct Answer: A — 20W

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Q. What is the power dissipated in a 4 ohm resistor carrying a current of 3 A?

A. 12 W
B. 9 W
C. 6 W
D. 3 W

Solution

Using the power formula P = I^2 * R, we have P = (3 A)^2 * 4 ohms = 9 * 4 = 36 W.

Correct Answer: A — 12 W

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Q. What is the power dissipated in a resistor of 10 ohms carrying a current of 2 A?

A. 20 W
B. 10 W
C. 5 W
D. 40 W

Solution

Using the power formula P = I^2 * R, we have P = (2 A)^2 * 10 ohms = 4 * 10 = 40 W.

Correct Answer: A — 20 W

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Q. What is the power dissipated in a resistor of 5Ω carrying a current of 2A?

A. 5W
B. 10W
C. 20W
D. 40W

Solution

Power is given by P = I^2 * R = (2A)^2 * 5Ω = 4A^2 * 5Ω = 20W.

Correct Answer: B — 10W

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Q. What is the power dissipated in a resistor of 5Ω carrying a current of 3A?

A. 15W
B. 9W
C. 5W
D. 3W

Solution

Power P = I^2 * R = (3A)^2 * 5Ω = 9A^2 * 5Ω = 45W.

Correct Answer: A — 15W

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Q. What is the total current flowing through a circuit if the total voltage is 12 V and the total resistance is 4 ohms?

A. 3 A
B. 4 A
C. 12 A
D. 48 A

Solution

Using Ohm's Law, I = V / R. Here, I = 12 V / 4 ohms = 3 A.

Correct Answer: A — 3 A

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Q. What is the total current flowing through a circuit if the total voltage is 12V and the total resistance is 4Ω?

A. 2A
B. 3A
C. 4A
D. 6A

Solution

Using Ohm's Law (I = V/R), the current is I = 12V / 4Ω = 3A.

Correct Answer: B — 3A

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Q. What is the total current flowing through a circuit if the total voltage is 24V and the total resistance is 6Ω?

A. 2A
B. 4A
C. 6A
D. 8A

Solution

Using Ohm's Law, I = V/R = 24V / 6Ω = 4A.

Correct Answer: B — 4A

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Q. What is the total current flowing through a circuit with a 10V battery and two 5Ω resistors in series?

A. 0.5A
B. 1A
C. 2A
D. 5A

Solution

Total resistance R = R1 + R2 = 5Ω + 5Ω = 10Ω. Using Ohm's law, I = V/R = 10V/10Ω = 1A.

Correct Answer: B — 1A

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Q. What is the total current flowing through a circuit with a 10V battery and two 5Ω resistors in parallel?

A. 1A
B. 2A
C. 5A
D. 10A

Solution

Equivalent resistance R_eq = 1/(1/5 + 1/5) = 2.5Ω. Total current I = V/R_eq = 10V/2.5Ω = 4A.

Correct Answer: B — 2A

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Q. What is the total current flowing through a junction where 5A enters and 3A and 2A leave?

A. 0A
B. 2A
C. 3A
D. 5A

Solution

According to Kirchhoff's Current Law, the total current entering a junction equals the total current leaving. Here, 5A = 3A + 2A.

Correct Answer: A — 0A

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Q. What is the total current in a circuit with a 12V battery and a total resistance of 3 ohms?

A. 4 A
B. 2 A
C. 3 A
D. 1 A

Solution

Using Ohm's law, I = V/R, we have I = 12V / 3 ohms = 4 A.

Correct Answer: A — 4 A

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Q. What is the total current in a circuit with a 12V battery and three resistors (R1 = 4Ω, R2 = 4Ω, R3 = 4Ω) connected in parallel?

A. 3A
B. 4A
C. 2A
D. 1A

Solution

Total resistance R_eq = 1 / (1/R1 + 1/R2 + 1/R3) = 1 / (1/4 + 1/4 + 1/4) = 1.33Ω. Current I = V / R_eq = 12V / 1.33Ω ≈ 9A.

Correct Answer: B — 4A

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Q. What is the total current in a circuit with a 24V battery and three resistors (2Ω, 4Ω, and 6Ω) connected in series?

A. 2A
B. 3A
C. 4A
D. 6A

Solution

Total resistance R = R1 + R2 + R3 = 2Ω + 4Ω + 6Ω = 12Ω. Using Ohm's law, I = V/R = 24V / 12Ω = 2A.

Correct Answer: B — 3A

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Q. What is the total power consumed in a circuit with a current of 5A and a total resistance of 4Ω?

A. 10W
B. 20W
C. 30W
D. 40W

Solution

Power (P) = I^2 * R = 5^2 * 4 = 25 * 4 = 100W.

Correct Answer: D — 40W

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Circuits & Kirchhoff Laws

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