A cell of emf 1.5 Vis connected with an external resistance `2Omega`. The potential difference falls to 1.0 v. The internal resistance of cell is

Options

A. `1.5 Omega`
B. `1.0 Omega`
C. `10.0 Omega`
D. `2.0 Omega`

Answer

C

Explanation

For a cell, E = V + Ir and V = IR`

` rArr (E -V)/V = (Ir)/(IR) = r/R`
` rArr ( E- V)/V = r/R`
`rArr (1.5 - 1.0)/(1.0) = r/ 20`
`rArr r = (20 xx 0.5)/10 = 10 Omega`