Measurement of Resistance using D.C. Bridges

D.C. bridges are electrical circuits used to measure resistance, capacitance, inductance, and impedance. However, they are mainly used for resistance measurement. The bridges work on the principle of null deflection, where the bridge is adjusted to equalize the voltage or current in the two arms of the circuit. When the bridge is balanced, the unknown resistance can be calculated from the known values of the other resistances in the circuit.

The four most commonly used D.C. bridges for resistance measurement are:

1. Wheatstone Bridge: It is the most commonly used bridge circuit for measuring resistance. It consists of four resistors arranged in a diamond configuration, with the unknown resistance connected in one arm of the bridge.

2. Kelvin Bridge: It is a modification of the Wheatstone bridge, used to measure low resistances accurately. It uses four resistors along with two additional resistors to nullify the effect of the lead resistance.

3. Maxwell Bridge: It is used to measure inductance, but it can also measure resistance by using a variable capacitor in one arm of the bridge.

4. Hay Bridge: It is used to measure the resistance of an inductor, but it can also measure resistance by using a variable capacitor in one arm of the bridge.

Conclusion

Thus, D.C. bridges are used for measuring resistance, capacitance, inductance, and impedance. However, they are mainly used for resistance measurement, and the four most commonly used D.C. bridges for resistance measurement are Wheatstone Bridge, Kelvin Bridge, Maxwell Bridge, and Hay Bridge.