In Wheatstone bridge galvanometer is used as a

Question

Examoogle · Accepted Answer

Null detector

Explanation: In a Wheatstone bridge circuit, the galvanometer serves as a null detector to identify the condition of bridge balance. When no current flows through the galvanometer, the bridge is balanced, indicating that the ratio of resistances in the arms is equal.

Working Principle: The Wheatstone bridge operates by balancing two potential dividers. When the potential at the two midpoints connected to the galvanometer is equal, the potential difference across the galvanometer becomes zero. The galvanometer detects this 'null' point, signaling that the unknown resistance can be calculated based on the balanced arm ratios.

Key Formulas: $\frac{P}{Q} = \frac{R}{S}$ — Condition for balanced Wheatstone bridge; $V_g = V_c - V_d = 0$ — Null condition for galvanometer

Key Points: A bridge is balanced when the current $I_g$ through the galvanometer is zero.; The sensitivity of the bridge depends on the galvanometer resistance and the source voltage.; It is primarily used for the precise measurement of medium-range resistances.

Advantages: High precision for resistance measurement; Independent of the absolute values of the source voltage

Disadvantages: Not suitable for very low (requires Kelvin Double Bridge) or very high resistance measurement; Requires manual adjustment to find the null point

Applications: Measurement of strain gauges in transducers; Precision resistance measurement in laboratory environments

Additional Info: The galvanometer does not supply power to the circuit; it merely monitors the potential difference.. Option A (Current source) and Option B (Voltage source) are incorrect because the bridge requires an external supply (like a battery) for excitation.

Answer: C is correct — In a Wheatstone bridge, the galvanometer acts as a sensitive null detector to indicate the state of balance.

Exam Tip: Always remember that in any bridge circuit (Wheatstone, Maxwell, Hay), the central branch is always a null-detection device, not an active power supply.

Related Questions

Discussion (0)