Question

A meter bridge is used to predict the value of unknown resistance $X$, it is observed that current is flowing from $A$ to $B$ initially $($when jockey is fixed at point $B)$. If the temperature of $X$ is increased, then select possible option/s.

• A. Current reduces in magnitude
• B. Current remain constant
• C. Current becomes zero
• D. Current flows in opposite direction

Answer 1

Answer: (A), (C), (D)

Current flows in opposite direction

As temperature of resistance increases magnituse of value of resistance $X$ increases.

For meter bridge condition
$\text{If}X(1-l)<Rl\text{then}{V}_A>V_B,$ current flows from $A$ to $B$

As $X$ is increased then, the inequality $X(1-l)<Rl$ may hold true but current may decrease (As $V_A-V_B$ decreases)

If $X$ is further increased then, meter bridge might reach balanced condition $X(1-l)=Rl$, current becomes zero (As $V_A=V_B$)

On further increasing value of $X$ increasing, meter bridge might reach condition obeying $X(1-l)>Rl$. Hence current may reverse its direction ie $B$ to $A$, here magnitude of current may increase or decrease((As $V_A<V_B$))