Question

The length of a wire is doubled. By what factor does

the resistance change

(a) 4 time as large
(b) twice as large

(c) unchanged
(d) half as large​

Answer 1

If you double the Length of wire and halved its radius.The Resistance increases 1/2 times of its usual Resistance.

Option (D) is correct.

Explanation:

We know that:

• R = ९ L/A
• ९ = Specific Resistivity
• L = Length
• A = Cross sectional area.

If the conductor is circular then:

A = π r^2

Now according to your assumption.

Length = 2L

Area = π (2r)^2 = π 4r^2 = 4A

Now

R = ९ 2L/4A

R = ९ L / 2A

Therefore , if you double the Length of wire and halved its radius.

The Resistance increases 1/2 times of its usual Resistance.

Also learn more

Calculate the resistance of a 5 m length of a wire of area of cross section 0.01 mm2 and resistivity 50×10^8 ohm metre ?

https://brainly.in/question/4552934

Answer 2

The length of a wire is doubled. The factor by which its resistance changes is 2 times. (Option b)

1) By the definition of resisitance we know, resistance is directly proportional to resistivity and length of the wire.

2) resistance is also inversely proportional to the cross sectional area of the wire.

3) according to the given condition,

L' = 2L

4) So, new resistance R' = 2R. Therefore, option b is the correct choice.