In the circuit shown, a meter bridge is in its balanced state. The meter bridge wire has a resistance `.1 ohm//cm`. The value of unknown resistance `X` and the current drawn from the battery of negligible resistance is

Options

A. 1A
B. 1.5A
C. 2A
D. 5A

Answer

A

Explanation

According to question,
`l_1/l_2=2/3`
For potentiometer , `R^1/R^2=l_1/l_2=2/3`
`x/6=2/3`
`Rightarrow x=4Omegam^-1`
Total resistance of known and unknown resistance = `6+4=10Omega`
The resistance of wire is `0.1xx 100Omega` = 102
So, effective resistance Re is given by `1/R_(eff)=1/10+1/10`
`Rightarrow R_(eff)=5Omega` Hence, current drawn from the battery is given by Ohm's law VlR
`Rightarrow l=V/R=5/5=1A`