Question

in the experiment of potentiometer the EMF of cell 2 volt negligible internal resistance is connected in primary circuit with 10 metre wire of potentiometer whose resistance is 20 ohm if potential gradient is obtained 5 microcoulomb per centimetre then what resistance should be introduced from rohestat​

Answer 1

Answer:

Resistance of wire, R = 20 ohm

EMF, E = 2V

Length, l = 10m

If I understand the question correctly then potential gradient can't be C/m, rather it is V/m. So, I'll correct the question as

Gradient, G = 5 uV/cm

Let the required resistance of rheostat be R'

Then current across wire, I = E/(R+R')

Then, 5 × 10^-6/10^-2 = (E/(R+R')).R/l

=> 5 × 10^-4 = 2/(20+R'). 20/10

=> 5(20+R') = 40000

=> R' = 7980 ohm = 7.98 Kiloohm