Question

AB is a wire of uniform resistance. The galvanometer G shows no deflection when the length AC = 20cm and CB = 80cm The resistance R is equal to

• A. 2$\Omega$
• B. 8$\Omega$
• C. 20$\Omega$
• D. 40$\Omega$

Answer 1

Answer: (C)

20$\Omega$

As $AC+CB=20+80=100cm=1m$ so it is a meter bridge.

The balance condition for this meter bridge is $\frac{R}{80}=\frac{AC}{100-AC}$

or $\frac{R}{80}=\frac{20}{100-20}$

$\therefore R=20\Omega$