Question

The resistance in Wheatstone's Bridge circuit shown in the figure have different values. The current through the galvanometer is zero. If all thermal effects are negligible, the current through the galvanometer will not be zero, when

• A. the battery emf is doubled
• B. the battery and galvanometer are interchanged
• C. all resistances in the circuit are doubled
• D. resistances $R_{1}$ and $R_{2}$ are interchanged

Answer 1

Answer: (D)

Wheatstone bridge is balanced. Then the required condition is
$\Rightarrow \frac{R_{1}}{R_{2}}=\frac{R_{3}}{R_{4}}$
If $R_{1}$ and $R_{2}$ are exchanged, the condition will no more hold good, then current will go through the galvanometer. For all the other cases, the condition holds good, so Wheatstone bridge will remain balanced.