Question

The diagram below shows a cardboard on which iron filings are kept. A wire bent in the form of a loop is seen passing through the cardboard. When current flows through it, the iron filings arrange themselves as shown below.

1. State the polarities of the battery at A and B.
2. State the effect on the magnetic field if an iron rod is held along the axis of the coil.
3. State one way to:
   1. Change the polarity of the coil.
   2. Decrease the strength of the magnetic field around the coil.

Answer 1

1. Positive and negative polarity are found at terminals A and B, respectively.
2. If an iron rod were held parallel to the coil's axis, the strength of the magnetic field would rise.
3. 
   
   1. Switching the positions of terminals A and B would cause the coil's polarity to alter.
   2. The magnetic field surrounding the coil would weaken as the current flowing through it decreased.