Question

The Wheatstone bridge is an arrangement of four resistances, say \(R_1, R_2, R_3\), and  \(R_4\). The null point condition is given by:

• A. \(\quad \frac{R_1}{R_2} = \frac{R_3}{R_4} \\\)
• B. \(\quad R_1 + R_2 = R_3 + R_4 \\\)
• C. \(\quad R_1 - R_2 = R_2 - R_4 \\\)
• D. \(\quad R_1 \times R_2 = R_3 \times R_4\)

Answer 1

The Correct Option is A

The Wheatstone bridge is a circuit used to measure unknown resistances by balancing two legs of a bridge circuit. By using four resistors, labeled as \(R_1\), \(R_2\), \(R_3\), and \(R_4\), the condition for which the bridge is balanced (known as the null point condition) can be determined. The meter shows no deflection at this point, indicating that the bridge is in equilibrium. The correct null point condition is: 

\[\frac{R_1}{R_2} = \frac{R_3}{R_4}\]

This equation implies that the ratio of the resistance values on one side of the bridge is equal to the ratio on the other side. This fundamental condition allows for the determination of an unknown resistance if the other resistances are known, making the Wheatstone bridge a valuable tool in electrical measurements.

Answer 2

The Wheatstone bridge is a circuit used to precisely measure an unknown resistance by balancing two legs of a bridge circuit. The bridge is composed of four resistors: \(R_1\), \(R_2\), \(R_3\), and \(R_4\). The bridge is said to be balanced or at a null point when no current flows through the galvanometer connected across its diagonal.

The null point condition for the Wheatstone bridge is derived from the concept that the potential difference between the two midpoints of the resistors in each leg should be the same. The null condition is given by:

\(<\frac{R_1}{R_2}=\frac{R_3}{R_4}>\)

This equation essentially states that the ratio of the resistances in one leg of the bridge should be equal to the ratio of the resistances in the other leg. Under this condition, the potential difference is zero, and the galvanometer shows no deflection