Terminal voltage of battery of `1.25 V and emf of battery" 1.5V , ` so internal resistance of battery is ...... `Omega`.

Options

A. 2
B. 20
C. 200
D. 2000

Answer

D

Explanation

2000
V = E - Ir
`= E - (Er)/(R + r) = (ER + Er - Er)/(R + r)`
`therefore V =(ER)/(V) `
`therefore R + r = (ER)/(V)`
`therefore r = (ER)/(V) - R`
` = (1.5 xx 10^(4))/(1.25) - 10^(4)`
= ` 1.2 xx 10^(4) - 10^(4) = 0.2 xx 10^(4)`
`therefore r = 2000 Omega`