Question

The potentiometer wire $AB,$ shown in fig, is $50cm$ long. When $AD=30cm$, no deflection occurs in the galvanometer. The value of ${}^{\prime }{R}^{\prime }$ is:

• A. $4\Omega$
• B. $8\Omega$
• C. $12\Omega$
• D. $2\Omega$

Answer 1

The correct option is A $4\Omega$

$6\times DB=R\times AD$

$\frac{6}{AD}DB=R$

$\frac{6\times 20}{30}=4\Omega$