Question

A 8 ohm resistance wire is doubled up by folding what is the value of new resistance

Answer 1

r=p×l/A

a=2a

l=l/2

r new p(l)/2/2a

r new=pl/4a

r new =r/4

r new =8/4

hence ans=2 ohm

Answer 2

Given,

Resistance of a wire=8 ohm

The wire is doubled up by folding

To Find,

Its new resistance.

Solution,

Here, R=8 ohms

We have the formula that,

   R=ρl/A

If wire is doubled so,

    Area A=2A

Then, here length will be,

            l=l/2

Then new resistance will be:

R new=ρ(l/2)/2A

⇒R new=ρl/4A

⇒R new=R/4(from the above formula)

⇒R new=8/4=2ohms

Hence, new resistance of wire is 2 ohms.