Short Answer

Resistance is measured using a Wheatstone Bridge by balancing two legs of a bridge circuit. When the bridge is balanced, no current flows through the galvanometer, and the unknown resistance can be calculated.

This method is very accurate and widely used in electrical engineering. It works on the principle of comparing an unknown resistance with known resistances.

Detailed Explanation:

Resistance Measurement using Wheatstone Bridge

Working Principle

The Wheatstone Bridge is a circuit used to measure an unknown resistance by comparing it with known resistances. It consists of four resistors arranged in a bridge form, along with a galvanometer and a voltage source.

Out of the four resistors, three are known and one is unknown. The unknown resistance is calculated by adjusting the known resistors until the bridge becomes balanced.

The bridge is said to be balanced when no current flows through the galvanometer. At this condition, the voltage across the galvanometer becomes zero.

The balance condition of the Wheatstone Bridge is given by the relation:

R1 / R2 = R3 / Rx

Where:
R1 and R2 are known resistances
R3 is a variable resistance
Rx is the unknown resistance

By rearranging the formula, the unknown resistance can be calculated as:

Rx = (R2 × R3) / R1

This formula is used to find the value of the unknown resistance accurately.

Measurement Process

To measure resistance using a Wheatstone Bridge, first the circuit is connected properly with all four resistors, a galvanometer, and a battery.

Then, the known resistances are set, and the variable resistor is adjusted slowly. While adjusting, the galvanometer is observed carefully.

When the galvanometer shows zero deflection, it means the bridge is balanced. At this point, the ratio of resistances in one branch is equal to the ratio in the other branch.

Now, the value of the unknown resistance can be calculated using the balance condition formula.

This method is highly accurate because it does not depend on the actual value of current or voltage. It only depends on the ratio of resistances.

Wheatstone Bridge is commonly used in laboratories and industries for precise measurement of medium resistances.

It is also used in sensor applications, such as strain gauges and temperature measurement devices.

The main advantage of this method is its high accuracy and sensitivity. However, it may not be suitable for very high or very low resistances.

Proper connection and careful adjustment are necessary to get accurate results. Any error in reading or connection can affect the measurement.

Conclusion

Wheatstone Bridge is an accurate method for measuring unknown resistance by balancing a bridge circuit. It works on the principle of comparing known and unknown resistances. Due to its high accuracy, it is widely used in electrical engineering applications.