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The source of error in a Wheatstone bridge is due to
Range of galvanometer used
Type of the source of emf used
Limiting errors of the three known resistances
Balance condition
Limiting errors of the three known resistances
Quick Summary: The primary source of measurement error in a Wheatstone bridge circuit arises from the inherent limiting errors (or tolerance levels) associated with the three known resistances used in the bridge arms. Since the unknown resistance is calculated based on the balanced ratio of these three, any deviation in their nominal values directly propagates into the calculated value of the unknown resistance.
The primary source of measurement error in a Wheatstone bridge circuit arises from the inherent limiting errors (or tolerance levels) associated with the three known resistances used in the bridge arms. Since the unknown resistance is calculated based on the balanced ratio of these three, any deviation in their nominal values directly propagates into the calculated value of the unknown resistance.
RxтАЛ=R1тАЛR2тАЛR3тАЛтАЛ тАФ Balance condition for unknown resistance
RxтАЛ╬ФRxтАЛтАЛ=R1тАЛ╬ФR1тАЛтАЛ+R2тАЛ╬ФR2тАЛтАЛ+R3тАЛ╬ФR3тАЛтАЛ тАФ Relative limiting error propagation
The Wheatstone bridge operates on the null-detector principle where RxтАЛ=R1тАЛR2тАЛR3тАЛтАЛ. Because each resistor R1тАЛ,R2тАЛ,R3тАЛ has an associated tolerance (e.g., ┬▒0.1%), the resultant error in RxтАЛ is the cumulative effect of these individual component uncertainties. Total relative error is approximately the sum of the relative errors of the three known resistors.
The Wheatstone bridge is a highly accurate null-deflection method.
Limiting errors refer to the guaranteed maximum deviation from the nominal value.
Sensitivity of the bridge depends on the galvanometer, but error originates from resistors.
Thermal EMF and contact resistance also contribute to errors, but component tolerance is the primary limiting factor.
High accuracy for medium-range resistance measurements
Simple circuit configuration based on ratio arms
Not suitable for very low resistance measurement due to lead/contact resistance
Not suitable for very high resistance measurement due to sensitivity issues
Precision resistance measurement in laboratories
Strain gauge instrumentation
The limiting error of the bridge is generally the summation of the errors of the three ratio-arm resistors.
Option A is incorrect because the galvanometer affects sensitivity, not the static error of the bridge balance.
Option B affects noise levels, not the basic resistance balance accuracy.
Option D is the ideal state and is not a source of error.
C is correct тАФ The accuracy of the bridge is constrained by the manufacturing tolerance of the three known resistors in the ratio arms.
Always remember that in bridge circuits, component tolerance (limiting error) is a multiplicative factor in the final result, whereas thermal noise is an additive factor.