i p K (b) Figure . Faraday’s second experiment 12th - 12th - - - - - Unit ELECTROMAGNETIC INDUCTION AND ALTERNATING CURRENT direction and hence an electric current flows in opposite direction (Figure . (b)). So there is deflection in the galvanometer when there is a relative motion between the coil and the magnet.
In the second experiment, when the primary coil P carries an electric current, a magnetic field is established around it. The magnetic lines of this field pass through itself and the neighbouring secondary coil S . When the primary circuit is open, no electric current flows in it and hence the magnetic flux linked with the secondary coil is zero (Figure . (a)).
However, when the primary circuit is closed, the increasing current builds up a G (a) G Right deflection magnetic flux linked is less magnetic flux linked is more (b) G G Lef deflection Figure . Explanation of Faraday’s first experiment Based on this idea, Faraday’s experiments are understood in the following way. In the first experiment, when a bar magnet is placed close to a coil, some of the magnetic field lines of the bar magnet pass through the coil i.e., the magnetic flux is linked with the coil. When the bar magnet and the coil approach each other, the magnetic flux linked with the coil increases.
So this increase in magnetic flux induces an emf and hence a transient electric current flows in the circuit in one direction (Figure . (a)). At the same time, when they recede away from one another, the magnetic flux linked with the coil decreases. The decrease in magnetic flux again induces an emf in opposite 12th - 12th - - - - - Unit ELECTROMAGNETIC INDUCTION AND ALTERNATING CURRENT magnetic field around the primary coil.
Therefore, the magnetic flux linked with the secondary coil increases. This increasing flux linked induces a transient electric current in the secondary coil (Figure . (b)). When the electric current in the primary coil reaches a steady value,