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D.C. bridges are used for
Measurement of resistance
Measurement of capacitance
Measurement of current
Measurement of inductance
Measurement of resistance
Quick Summary: D.C. bridges, such as the Wheatstone bridge, are fundamental electrical instruments used specifically for the precision measurement of unknown resistances. They operate on the principle of a null-balance circuit where an unknown resistance is determined by balancing the bridge arms under steady-state direct current conditions.
D.C. bridges, such as the Wheatstone bridge, are fundamental electrical instruments used specifically for the precision measurement of unknown resistances. They operate on the principle of a null-balance circuit where an unknown resistance is determined by balancing the bridge arms under steady-state direct current conditions.
RxтАЛ=R3тАЛтЛЕR1тАЛR2тАЛтАЛ тАФ Standard balance equation for a Wheatstone bridge
QPтАЛ=SRтАЛ тАФ Condition of bridge balance where S is the unknown
The bridge consists of four arms forming a closed loop with a DC supply connected across one pair of nodes and a null detector (galvanometer) across the other. When the potential difference across the detector is zero, the bridge is balanced. At balance, the product of the resistances of opposite arms is equal, allowing for the precise calculation of an unknown resistor based on the ratio of known resistors.
D.C. bridges use a null-deflection method which is independent of the source voltage fluctuations.
The Wheatstone bridge is suitable for medium resistance measurements (1 ╬й to 100 k╬й).
Kelvin's Double Bridge is a modification of the Wheatstone bridge for low resistance measurements.
High accuracy due to null-balancing method.
Measurement is independent of the detector sensitivity once balanced.
Not suitable for high resistance measurements (requires megger).
Requires a stable DC source.
Calibration of resistors.
Strain gauge measurement systems.
Fault location in underground cables.
Option B (capacitance) and Option D (inductance) require A.C. bridges (like Maxwell or Schering bridge) because these components exhibit frequency-dependent reactance.
Option C is incorrect as bridges measure impedance/resistance, not current directly.
A is correct тАФ D.C. bridges are specifically designed to determine unknown resistance values by achieving a balanced potential state in a Wheatstone configuration.
Always remember that D.C. bridges cannot be used for AC parameters (L, C) because the reactive components do not produce a stable balance point under steady DC bias.