AN ideal battery of 4 V and resistance R are connected in series in the primary circuit of a potentiometer of length 1 m and and resistance 5Ω the value of R, to give a difference of 56mV across 10 cm of potentiometer wire , is :

Options

A. `490 Omega`
B. `480 Omega`
C. `395 Omega`
D. `495 Omega`

Explanation

Potential gradient =`(5 times 10^-3)/(10 times 10^-2)=(4/(R+5) times 5)`
`implies 1/20=20/(R+5)`
`implies 400=R+5 implies 395 Omega`