Question

With a certain resistance in the left gap of the slide wire metre bridge the balance point is obtained when resistance of 10 ohm is taken out from resistance box on increasing the resistance from resistance box by 12.5 ohm the balance point shift by 20 cm find unknown resistance.

Answer 1

With a certain resistance in the left gap of the slide wire metre bridge the balance point is obtained when resistance of 10 ohm is taken out from resistance box on increasing the resistance from resistance box by 12.5 ohm the balance point shift by 20 cm find unknown resistance.

Explanation:

Let unknown resistance be X. In first case, if  l is the balancing length then,

X/R = l/ (100-l)

∴ X = 10l/ (100-l)   ......1

In the second case, R = 10 + 12.5

=22.5Ω

and l'  = l-20

∴ X/R  = l' /(100-l) ...2

or X = 22.5

When we solve  equations (1) and (2) we will get   l = 60 cm and X = 15Ω