JEE Main & Advanced Physics Current Electricity, Charging & Discharging Of Capacitors / वर्तमान बिजली, चार्ज और कैपेसिटर का निर JEE PYQ-Current Electricity Charging and Discharging of Capacitors

The current in the primary circuit of a potentiometer is 0.2 A. The specific resistance and cross-section of the potentiometer wire are \[4\times {{10}^{-7}}\]ohm metre and \[8\times {{10}^{-7}}{{m}^{2}}\]respectively. The potential gradient will be equal to: [AIEEE 11-05-2011]

A) 1 V/ m

B) 0.5 V/m

C) 0.1 V/m

D) 0.2 V/m

Correct Answer: C

Solution :

[c] \[x=\frac{V}{\ell }=\frac{IR}{\ell }=\frac{IR}{\ell }\left( \frac{\rho \ell }{A} \right)=\frac{I\rho }{A}\]

\[x=\frac{0.2\times 4\times {{10}^{-7}}}{8\times {{10}^{-7}}}=\frac{0.8}{8}=0.1\,V/m.\]