Question

A narrow copper wire of length L and radius b is attached to a wide copper wire of length L and radius 2b, forming one long wire of length 2L. This long wire is attached to a battery, and a current is flowing through it. If the electric field in the narrow wire is E, the electric field in the wide wire is:______

a. E
b. 2E
c. 4E
d. E/2
e. E/4

Answer 1

Correct answer is E/4.

Explanation:ρ

by the formula of
`R=(\rho L)/(A)`

Now,
`R_(1) = (\rho L)/(\pi b^(2)) \\ R_(2) = (\rho L)/(4\pi b^(2))`

and,
`R_(1)=4R_(2)`

The wires are connected in series so the current will be same. So, by the
`V=iR` formula

`V_(1)=4{V_(2)`

similarly,

`E_(1)=4E_(2)\\E=4E_(2)\\E_(2)=(E)/(4)`