Question

Why should the area of cross-section of the meter bridge wire be uniform?

Answer 1

An electrical appliance that is used to calculate the resistance of metal coil more accurately is called Meter Bridge. The principle behind the Meter Bridge works is the Wheatstone bridge. It is an electrical network that is used to calculate the value of unknown resistance. The Wheatstone bridge circuit will basically have four resistances that are connected together.

Complete answer:
As we already said we use Meter Bridge to calculate the resistance more accurately. The question that is asked is why do the meter bridge’s area of the cross-section is uniform?
First, we need to see what uniform cross-section is. If the shape and the size of the cross-section at every point along the length or breadth or height of the solid then we can say the solid’s cross-section is uniform.
Now the area of the cross-section of the meter bridge wire should be uniform because if we suppose it is not having a uniform cross-section then the value of the resistance per unit length will be having different values over a different length of Meter Bridge. If the area of the cross-section of the meter bridge is uniform then the same resistance will be maintained throughout the conductor and therefore we can obtain accurate measurements of resistances.

Note:
In the meter bridge among the four resistances, one pair is replaced by the wire of uniform cross-section of about $1m$. The other pair consists of two resistances of which one is known and the other is unknown. The galvanometer will be connected between the two resistances and the other part will be connected to the wire in which the null point is found. At this exact point where the galvanometer shows zero deflection is the point where the wheat stone bridge is said to be balanced.