Question

A 10 m long wire of uniform cross-section and 20 Ω resistance is used in a potentiometer. The wire is connected in series with a battery of 5 V along with an external resistance of 480 Ω. If an unknown emf E is balanced at 6.0 m length of the wire, then the value of unknown emf is ______.

विकल्प

• 1.2 V

• 1.02 V

• 0.2 V

• 0.12 V

Answer 1

A 10 m long wire of uniform cross-section and 20 Ω resistance is used in a potentiometer. The wire is connected in series with a battery of 5 V along with an external resistance of 480 Ω. If an unknown emf E is balanced at 6.0 m length of the wire, then the value of unknown emf is 0.12 V.

Explanation:

Let PQ is a potentiometer wore of length 10 m,

I = `"E"/("R" + "R'") = 5/(480 + 20) = 5/500`

`= 1/100 = 0.01 "A"`

`"V"_"PQ" = "IR"_"PQ" = 0.01 xx 20` = 0.2 V

If 10 m potentiometer wire balance ⇒ 0.2 V

Then 1 m potentiometer wire balances ⇒ `0.2/10`V

Then 6 m potentiometer wire balances `0.2/10 xx 6 "V"`

`= 1.2/10 = 0.12`V