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A potentiometer wire, 10 m long, has a r...

A potentiometer wire, 10 m long, has a resistance of `40Omega`. It is connected in series with a resistance box and a 2 v storage cell. If the potential gradient along the wire is (0.1 mV/cm), the resistance unplunged in the box is

A

A)`260Omega`

B

B)`760Omega`

C

C)`960Omega`

D

D)`1060Omega`

Text Solution

Verified by Experts

The correct Answer is:
B
Potential gradient along wire
`=("Potential difference alonga wire")/("Length of wire")`
`therefore 0.1xx10^(-3)=(Ixx40)/(1000)V//cm`
Current in wire `I=(1)/(400)A`
or `I=(E)/(R+R.)`
`therefore (2)/(40+R)=(1)/(400)`
or `R=800-40`
`=760Omega`
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