Question

In a potentiometer experiment, a wire of length 10m having resistance 2ohm per metre is connected with a cell of 5V ,1ohm and an unknown resistance R. If potential gradient of wire is 2mV/cm ,then value of R is.
(1) 30 (2) 3 (3) 29 (4) 50

Answer 1

Answer: 29

Explanation: R= 2ohm per unit length

=>. R for 10 m = 2×10 =20ohm

=>. Potential gradient =V/L= 2mV/cm

=>. = 1/5 V/m

=>. I = V/ Req

=>. I=5/1+20+r

=>. I=5/21+r

=>. V. = IR

=>. V= 5/21+r × 20

=>. V= 100/21+r

=>. V/L. = 10/21+r

=>. 1/5. =. 10/21+r

=>. 21+r =. 50

=>. R = 29 ohm

Answer 2

The value of r is 30ohm.

Hope this will be helpful for you.