Sources of error
- The jockey should not be rubbed on the wire, as this resistance of wire will not remain uniform.
- Current should not be allowed to flow in the wire for a long time as this by producing heat will change the resistance of the wire.
- The value of resistor R is so selected that the null point is in the middle of the wire. Actually by doing so the error in the measurement is minimized. Also then all the four resistors are of the same order.