A cell ofemf E volt with no internal resistance is connected to a wire whose cross section chages. The wire has three sections of equal length. The middle section has a redius a, whereas the radius of the outer two sections is 2a. The raito of the potential differece across section AB to the potential differecne across section CA is

Options

A. 5
B. 4
C. `1//2`
D. `1//4`

Answer

B

Explanation

in series combination, I is costant, therefore `V propR.`
`(V_(AB))/(V_(CA))=(R_(AB))/(R_(CA))=(rho(I)/(pia^2))/(rho(I)/(pi(2a)^(2)))=(4)/(1)`