A potentiometer having the potential gradient of `2 mV//cm` is used to measure the difference of potential across a resistance of `10 ohm`. If a length of `50 cm` of the potentiometer wire is required to get null point, the current passing through the `10 ohm` resistor is (in `mA`)

Options

A. 1
B. 2
C. 5
D. 10

Answer

4

Explanation

Potential gradient `k=2(mV)/(cm)`
`therefore` potential difference `V=kl=2xx50=100mV`
Resistance R=`10Omega`
`therefore` Current `l=(V)/(R)=(100xx10^(-3))/(10)=10mA`.