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Question (21)

QN0036392

A wire is replaced by another wire of the same material and length but twice the cross-sectional area. Its resistance becomes:

(A) Twice
(B) Half
(C) Four times
(D) Unchanged

Correct Answer: B

Explanation:

R = ρl/A. Doubling area makes resistance half.

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Question (22)

QN0036393

A wire of resistance 6 Ω is stretched so that its length becomes twice, while its volume remains constant. Its new resistance will be:

(A) 3 Ω
(B) 6 Ω
(C) 12 Ω
(D) 24 Ω

Correct Answer: D

Explanation:

Length doubles and area becomes half, so resistance becomes four times. New R = 24 Ω.

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Question (23)

QN0036394

A wire has resistance 10 Ω. If its length is reduced to half while its cross-sectional area remains unchanged, the new resistance is:

(A) 2.5 Ω
(B) 5 Ω
(C) 10 Ω
(D) 20 Ω

Correct Answer: B

Explanation:

Resistance is directly proportional to length, so new R = 5 Ω.

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Question (24)

QN0036395

Two wires of the same material have equal lengths. Wire A has twice the cross-sectional area of wire B. The ratio RA:RB is:

(A) 1:2
(B) 2:1
(C) 1:4
(D) 4:1

Correct Answer: A

Explanation:

Resistance is inversely proportional to cross-sectional area.

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Question (25)

QN0036396

The SI unit of resistivity is:

(A) Ω
(B) Ω m
(C) Ω/m
(D) V/A²

Correct Answer: B

Explanation:

The SI unit of resistivity is ohm metre (Ω m).

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Question (26)

QN0036397

A wire has resistance 4 Ω. Another wire of the same material has half the length and twice the area of cross-section. Its resistance is:

(A) 1 Ω
(B) 2 Ω
(C) 4 Ω
(D) 8 Ω

Correct Answer: A

Explanation:

R2/R1 = (l/2)/(2A) = 1/4, so R2 = 1 Ω.

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Question (27)

QN0036398

Three resistors of 2 Ω, 3 Ω and 5 Ω are connected in series. Their equivalent resistance is:

(A) 1 Ω
(B) 5 Ω
(C) 10 Ω
(D) 30 Ω

Correct Answer: C

Explanation:

Rs = 2 + 3 + 5 = 10 Ω.

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Question (28)

QN0036399

Two resistors of 4 Ω and 6 Ω are connected in series across a 20 V battery. The current in the circuit is:

(A) 1 A
(B) 2 A
(C) 5 A
(D) 10 A

Correct Answer: B

Explanation:

Total resistance = 10 Ω. I = 20/10 = 2 A.

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Question (29)

QN0036400

Three resistors of 5 Ω each are connected in series. The potential difference across the combination is 30 V. The current is:

(A) 1 A
(B) 2 A
(C) 5 A
(D) 6 A

Correct Answer: B

Explanation:

Total resistance = 15 Ω. I = 30/15 = 2 A.

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Question (30)

QN0036401

In a series combination of resistors, which quantity remains the same through every resistor?

(A) Potential difference
(B) Current
(C) Resistance
(D) Power

Correct Answer: B

Explanation:

The same current flows through every resistor in series.

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Question (21)

A wire is replaced by another wire of the same material and length but twice the cross-sectional area. Its resistance becomes:

Explanation:

Link:

Question (22)

A wire of resistance 6 Ω is stretched so that its length becomes twice, while its volume remains constant. Its new resistance will be:

Explanation:

Link:

Question (23)

A wire has resistance 10 Ω. If its length is reduced to half while its cross-sectional area remains unchanged, the new resistance is:

Explanation:

Link:

Question (24)

Two wires of the same material have equal lengths. Wire A has twice the cross-sectional area of wire B. The ratio RA:RB is:

Explanation:

Link:

Question (25)

The SI unit of resistivity is:

Explanation:

Link:

Question (26)

A wire has resistance 4 Ω. Another wire of the same material has half the length and twice the area of cross-section. Its resistance is:

Explanation:

Link:

Question (27)

Three resistors of 2 Ω, 3 Ω and 5 Ω are connected in series. Their equivalent resistance is:

Explanation:

Link:

Question (28)

Two resistors of 4 Ω and 6 Ω are connected in series across a 20 V battery. The current in the circuit is:

Explanation:

Link:

Question (29)

Three resistors of 5 Ω each are connected in series. The potential difference across the combination is 30 V. The current is:

Explanation:

Link:

Question (30)

In a series combination of resistors, which quantity remains the same through every resistor?

Explanation:

Link:

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