Q. 205.0( 4 Votes )

i. Define electro

Answer :

i) Electromagnetic induction is the generation or creation of electromotive force across an electrical conductor when there is a change in the magnetic field.


A. As Current in the coil P is started by closing the key there is a change in the associated magnetic field. This hence changes the magnetic field around region/coil Q too. Due to this there is a generation of induced electric current in the coil leading to the deflection of the galvanometer G.

B. As current continues to flow in coil P, there is no change in magnetic field or rather the magnetic flux does not change hence galvanometer shows no deflection.

C. When current in coil P is stopped by removing the key, current reaches to the zero value thus changing the associated magnetic field too due to change in current. This would bring about change in magnetic field around coil Q, electrical current gets induced and hence galvanometer shows deflection.


The activity to plot the magnetic field lines around the bar magnet employes iron fillings, iron fillings are used because iron is a magnetic material and it gets attracted by a magnet. The following steps are executed to demonstrate the activity: -

1. Fix a sheet of white paper on a drawing board using some adhesive material.

2. Place a bar magnet in the centre of it.

3. Sprinkle some iron filings uniformly around the bar magnet. A salt-sprinkler may be used for this purpose.

4. Now tap the board gently.

Observations The iron filings arrange themselves in a pattern as shown in the diagram. The magnet influences the filings in the region surrounding it. Therefore the iron filings experience a force. The force thus exerted makes iron filings to arrange in a pattern. The region surrounding a magnet, in which the force of the magnet can be detected, is said to have a magnetic field. The lines along which the iron filings align themselves represent magnetic field lines around the bar magnet.

A region A has magnetic field lines relatively closer than another region B. Therefore region A has more stronger magnetic field compared to region B because as we know that the strength of a magnetic field is directly proportional to the closeness of the field lines and since field lines are closer in region A hence it is having a stronger magnetic field.

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