Answer the following in Brief

Question

State any two sources of errors in meterbridge experiment. Explain how they can be minimized.

Accepted Answer

The chief sources of error in the metre bridge experiment are as follows :

The bridge wire may not be uniform in cross section. Then the wire will not have a uniform resistance per unit length and hence its resistance will not be proportional to its length.
End resistances at the two ends of the wire may be introduced due to
1. the resistance of the metal strips
2. the contact resistance of the bridge wire with the metal strips
3. unmeasured lengths of the wire at the ends because the contact points of the wire with the metal strips do not coincide with the two ends of the metre scale attached.

Such errors are almost unavoidable but can be minimized considerably as follows :

Readings must be taken by adjusting the standard known resistance such that the null point is obtained close to the centre of the wire. When several readings are to be taken, the null points should lie in the middle one-third of the wire.
The measurements must be repeated with the standard resistance (resistance box) and the unknown resistance interchanged in the gaps of the bridge, obtaining the averages of the two results.

Answer