Question

a wire of resistance 5 ohm is stretched slowly till its length is doubled then the resistance of the stretched wire is

Answer 1

Hey there !

Solution:

Formula to be used:

• Resistance = Resistivity × Length / Area

Given that the length is doubled. So let the original Length be 'x' and area of cross section be 'y'

So Old resistance = Resistivity × x / y => Equation 1

We know that, If length of a conductor doubles, then the area of the cross-section becomes half as they are inversely proportional.

Hence the area of cross section will become y / 2

So Resistance = Resistivity × 2x / y / 2

=> New Resistance = 2 × 2 × Resistivity × x / y

=> New resistance = 4 Old resistance. ( From Equation 1 )

Hence the new resistance = 4 × 5 = 20 Ω

Hope my answer helped !

Answer 2

Answer:

Explanation:

When the length is doubled, area is halved.

R=Resistivity*length/area

Let initial length be x units, initial area be y units.

After stretch, length is 2x and area is y/2 units as net volume of wire has to be constant.

Hence, the value becomes 4 times of original value after substituting new length and area in the formula.

So,20 ohms is the answer, hope you understood