Question

Potentiometer wire of length 1m is connected in series with $490\Omega$ resistance and 2 V battery. If 0.2 mV/cm is the potential gradient, then resistance of the potentiometer wire is

• A. $4.9\Omega$
• B. $7.9\Omega$
• C. $5.9\Omega$
• D. $6.9\Omega$

Answer 1

The correct option is A $4.9\Omega$

According to the question;

Potential gradient $x=\frac{e}{(R+R_h+r)}.\frac{R}{L}$

$\Rightarrow \frac{0.2\times {10}^{-3}}{{10}^{-2}}=\frac{2}{(R+490+0)}\times \frac{R}{1}\Rightarrow R=4.9\Omega$