The bulb in the circuit shown in Fig. does not glow. Can you identify the problem? Make necessary changes in the circuit to make the bulb glow.

The positive terminal (+) of one cell always be connected to negative terminal (-) of another cell. Here the two positive terminals are connected to each other. The correct arrangement is as follows:

Two identical circular loops \(P\) and \(Q\) each of radius \(r\) are lying in parallel planes such that they have common axis. The current through \(P\) and \(Q\) are \(I\) and \(4I\) respectively in clockwise direction as seen from \(O\). The net magnetic field at \(O\) is: 
Find magnetic field at midpoint O. Rings have radius $R$ and direction of current is in opposite sense. 

