In the circuit shown in figure, sliding contact is moving with uniform velocity towards right. Its value at some instance is $12\Omega$ The current in the circuit at this instant of time will be

Since resistance of the circuit is increasing and hence current in the circuit is decreasing, so di/dt is negative.
Current in the circuit is given by $i=\frac{6-L{\displaystyle \frac{di}{dt}}}{12}$
Since (di/dt) is negative so the value of numerator will be more than 6V and hence current in the circuit at that instant will be
more than 0.5 A.