Question

In the meter bridge shown, the resistance $X$ has a negative temperature coefficient of resistance. Neglecting the variation in other resistors, when current is passed for some time, in the circuit balance point should shift towards:

• A. $A$
• B. $B$
• C. First $A$ then $B$
• D. It will remain at $C$

Answer 1

The correct option is B $B$

We know that in meter bridge the balanced condition is :

$\frac{R}{X}=\frac{AC}{BC}$

now if some current is passed it means heat is produced, and temperature of X is increased and X has a negative temperature coefficient that means Resistance of X decreases.

$\frac{R}{X}=\frac{AC}{BC}$

Now X decreases, so as to maintain the ratio BC should also decrease or AC should increase so that balance point should shift towards B.