A 10m long potentiometer wire has a resistance of 20 ohm. It is connected in series with a battery of emf 3V and a resistance of `10Omega`. The internal resistance of cell is negligible. If he length can be read accurately up 10 1mm, the potentiometer can read voltage.

Options

A. up to minimum of 0.2 mV
B. with an accuracy of 0.2 mv
C. with an accuracy of 0.1 mV
D. up to minimum of 2V

Answer

B

Explanation

Current in wire `3/30 =0.1 A`
`V=IR =2V`
Maximum voltage can read =2V
`lambda=V/l =2/(10xx10^(3)) =0.2 m V//mm`
Least account of scale =1mm
accuracy =0.2 mV