Question

With resistances P and Q placed in the left and right gaps of a metre bridge, the balance point divides the wire in the ratio of 1/3. When P and Q are increased by 40 n each. the balance point divides the wire in the ratio of 3/5. The values of P and Q will be respectively, ______ 

Options

• 30 Ω, 10 Ω

• 10 Ω, 30 Ω

• 20 Ω, 60 Ω

• 60 Ω, 40 Ω

Answer 1

With resistances P and Q placed in the left and right gaps of a metre bridge, the balance point divides the wire in the ratio of 1/3. When P and Q are increased by 40 n each. the balance point divides the wire in the ratio of 3/5. The values of P and Q will be respectively, 20 Ω, 60 Ω.

Explanation:

`"P"/"Q" = 1/3` ⇒ Q = 3P

and `("P" + 40)/("Q" + 40) = 3/5`

∴ `("P" + 40)/(3"P" + 40) = 3/5`

∴ P = 20 Ω and Q = 3P = 60 Ω