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In Wheatstone bridge galvanometer is used as a
Current source
Voltage source
Null detector
Input impedance
Null detector
Quick Summary: 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.
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.
QPтАЛ=SRтАЛ тАФ Condition for balanced Wheatstone bridge
VgтАЛ=VcтАЛтИТVdтАЛ=0 тАФ Null condition for galvanometer
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.
A bridge is balanced when the current IgтАЛ 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.
High precision for resistance measurement
Independent of the absolute values of the source voltage
Not suitable for very low (requires Kelvin Double Bridge) or very high resistance measurement
Requires manual adjustment to find the null point
Measurement of strain gauges in transducers
Precision resistance measurement in laboratory environments
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.
C is correct тАФ In a Wheatstone bridge, the galvanometer acts as a sensitive null detector to indicate the state of balance.
Always remember that in any bridge circuit (Wheatstone, Maxwell, Hay), the central branch is always a null-detection device, not an active power supply.