The meter bridge, also known as the slide wire bridge consists of a 1-meter-long wire of uniform cross-sectional area, fixed on a wooden block. A scale is attached to the block. Two gaps are formed on it by using thick metal strips in order to make the Wheatstone bridge.

The meter bridge operates using the Wheatstone principle. Here, four resistors P, Q, R, and S are connected to form the network ABCD. Terminals A and C are connected to a battery, and the terminals B and D are connected to a galvanometer.

In the balancing condition, there is no deflection on the galvanometer. Then, $$\frac{P}{Q}=\frac{R}{S}$$

If a resistance wire of unknown resistance 𝑋 is introduced in the right gap of the meter bridge and the high resistance 𝑅 is introduced in the left gap of the meter bridge, then as the jockey slides over the bridge wire, it shows zero deflection at the balancing point (null point).

If the balancing length is 𝑙, then according to the Wheatstone principle, we have $$\frac{X}{R}=\frac{l}{100-l}$$

The unknown resistance is given by $$X=R \frac{l}{100-l}$$

The specific resistance of the wire can be calculated using the relation, $$\rho=\frac{\pi r^2 X}{L}$$

where, 𝐿 is the length of the wire and 𝑟 is its radius.

Requirements for this Science Experiment

⦁ Meter Bridge ⦁ Jockey ⦁ Resistance Box ⦁ Plug Key ⦁ Battery