Question

Assertion (A): In a Wheatstone bridge circuit, if we interchange the position of the cell and the galvanometer, the balance condition `P/Q = R/S` remains unchanged.

Reason (R): `P/Q = R/S ⇒ Q/S = P/R`, so balance condition remains same.

Options

• Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

• Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).

• Assertion (A) is true, but Reason (R) is false.

• Both Assertion (A) and Reason (R) are false.

Answer 1

Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

Explanation:

In a balanced Wheatstone bridge, the condition `P/Q = R/S` ensures that the potential difference across the galvanometer is zero, so no current flows through it. This equilibrium means the arms containing the cell and the galvanometer act as conjugate arms, where interchanging their positions does not disturb the balance. Since the bridge remains balanced even after exchanging the cell and the galvanometer, Assertion (A) is true.

From the fundamental balance condition `P/Q = R/S` we derive PS = QR, which can also be written as `Q/S = P/R`. This mathematical symmetry shows that swapping the cell and galvanometer leads to the same underlying ratio, proving that the balance condition remains identical in both cases. Thus, Reason (R) is true.

Hence, Reason (R) is true and correctly explains the Assertion.