In the circuit shows in Fig. `6.44`, the galvanometer `G` shows zero deflection. If the batteries `A` and `B` have negligible internal resistance, the value of the resistor `R` will be

Options

A. `200Omega`
B. `100Omega`
C. `500Omega`
D. `1000Omega`

Explanation

The galvanometer shows zero deflection, i.e., current through XY is zero
As a result potential drop across R is 2V. Circuit can be redrawn as
`I=12/(500+R)`
Voltage across R, V=IR `implies 2=12/(500+R) times R implies R=100 Omega`