12th Class Physics Current Electricity, Charging & Discharging Of Capacitors / वर्तमान बिजली, चार्ज और कैपेसिटर का निर Question Bank MCQs - Current Electricity

When cell of e.m.f. E is connected with an external resistance R, the p.d. across the cell becomes V. The expression for the internal resistance of the cell is

A) \[\frac{E\ -V}{V}R\]

B) \[{{10}^{23}}\]

C) \[\frac{V-E}{V}R\]

D) \[\frac{V-E}{\operatorname{E}}R\]

Correct Answer: A

Solution :

Option [a] is correct.

Explanation: Current in the circuit = I = V /R If r = internal resistance of the cell, then

V=E - Ir

\[\therefore \operatorname{r}=\frac{E\ -V}{I}=\frac{E\ -V}{V/R}=\frac{E\ -V}{V}R\]