SAMPLE QUESTIONS
1. Two circular, similar, coaxial loops carry equal currents in the same direction. If the loops are brought nearer, what will happen?
a) Current will increase in each loop
b) Current will decrease in each loop
c) Current will remain same in each loop
d) Current will increase in one and decrease in the other
2. There is a horizontal cylindrical uniform but time-varying magnetic field increasing at a constant rate dB/dt as shown in figure. A charged particle having charge q and mass m is kept in equilibrium, at the top of a spring of spring constant K, in such a way that it is on the horizontal line passing through the centre of the magnetic field as shown in figure. The compression in the spring will be
a) $\frac{1}{K}\left [ mg-\frac{qR^{2}}{2l}\frac{dB}{dt} \right ]$
b) $\frac{1}{K}\left [ mg+\frac{qR^{2}}{l}\frac{dB}{dt} \right ]$
c) $\frac{1}{K}\left [ mg+\frac{2qR^{2}}{l}\frac{dB}{dt} \right ]$
d) $\frac{1}{K}\left [ mg+\frac{qR^{2}}{2l}\frac{dB}{dt} \right ]$