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The arms consisting of the resistances RтВБ and RтВВ are called
Resistance arms
Impedance arms
Source arms
Ratio arms
Ratio arms
In a Wheatstone bridge circuit, the resistances R1тАЛ and R2тАЛ form the ratio arms, which determine the sensitivity and multiplication factor of the bridge. The balance condition of the bridge is determined by the ratio of these two arms relative to the other two arms (R3тАЛ and RxтАЛ).
In a Wheatstone bridge circuit, the resistances R1тАЛ and R2тАЛ form the ratio arms, which determine the sensitivity and multiplication factor of the bridge. The balance condition of the bridge is determined by the ratio of these two arms relative to the other two arms (R3тАЛ and RxтАЛ).
R2тАЛR1тАЛтАЛ=RxтАЛR3тАЛтАЛ тАФ Wheatstone bridge balance condition
RxтАЛ=R3тАЛтЛЕ(R1тАЛR2тАЛтАЛ) тАФ Expression for unknown resistance
The Wheatstone bridge operates on the null-deflection principle. When the bridge is balanced, the potential difference across the galvanometer is zero, leading to the condition R2тАЛR1тАЛтАЛ=RxтАЛR3тАЛтАЛ. By adjusting the ratio R2тАЛR1тАЛтАЛ, an unknown resistance RxтАЛ can be measured precisely.
The ratio arms R1тАЛ and R2тАЛ are typically fixed or selectable precision resistors.
The bridge sensitivity is optimized when the arms are chosen such that the ratio provides a suitable multiplication factor for the range of RxтАЛ.
In slide-wire bridges, these arms are segments of a single uniform wire.
High precision for medium resistance measurements
Eliminates errors due to internal supply variations at null point
Not suitable for extremely low or high resistances
Requires manual or automated balancing
Precision resistance measurement in laboratory environments
Strain gauge measurement circuits
Thermistor-based temperature sensing
The term 'Ratio arms' specifically refers to the pair R1тАЛ/R2тАЛ because their ratio determines the balance point independent of the absolute resistance values.
Option A is incorrect as 'resistance arms' is a generic term for all bridge arms.
Option B is incorrect as 'impedance arms' typically refers to AC bridges (like Maxwell or Hay bridge).
D is correct тАФ The pair of resistors R1тАЛ and R2тАЛ are known as the ratio arms because their ratio R2тАЛR1тАЛтАЛ defines the proportionality of the bridge at balance.
Always remember that in AC bridges (Impedance Bridges), the ratio arms may consist of complex impedances (Z1тАЛ/Z2тАЛ) instead of pure resistances.
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