Question

In a meter bridge the null point is found at distance of 33.7cm from A. If now a resistance of 12 Ω connected in parallel with S, the null point occurs at 51.9cm. Determine the values of Rand S.

Answer 1

 for meter bridge E∝ l ⇒ R ∝ l

From the first balance point, we get

After S is connected in parallel with a resistance of 12 Ω , the resistance across the gap changes form S to 

and hence the new balance condition now gives 

Substituting the value of R/S form Eq. (i), we get

Which gives S = 13.5Ω. Using the value of R/S above, we get R = 6.86Ω