Question

In a wheatstone bridge all the four arms have equal resistance r. If resistane of a galvonmeter arm is also r, then equicalent resistance of the combination is

Answer 1

Answer:

r

Explanation:

Since the bridge is balanced with equal resistances in all the four arms, resistance in the galvonometer arm doesnt matter.

In the balanced bridge, no current passes through the galvanometer arm and hence this arm doesnt contribute to effective resistance (or this arm offers infinite resistace).

So the effective resistance of the bridge is due to the contribution of the bridge arms. i.e. (r+r) || (r+r)

= r ohm

Alternatively, it can be shown that the effective resistance is r. See the image for the alternate method.