Physics
Explain the mechanism of attraction of iron nails by a magnet when brought near them.
Answer
If one pole of a bar magnet is brought near small iron nails, they form a chain of nails as shown below, because the bar magnet by induction magnetizes an iron nail which gets attracted to the magnet and clings to it. This magnetized nail magnetizes the other nail near it by magnetic induction and attracts it.
This process continues till force of attraction of magnet on first nail is sufficient to balance the total weight of all the nails in the chain below it.
Now holding the uppermost nail in position by fingers, and if the magnet is removed, we find that all nails fall down. The reason is that on removing the magnet, the uppermost nail loses it's magnetism, so all other nails also lose their magnetism, they get separated from each other and they all fall down due to the force of gravity.
This shows that the magnetism acquired by induction is purely temporary. It lasts so long as the magnet causing induction remains in it's vicinity.
Related Questions
Explain the method of plotting magnetic field lines by using a small compass needle.
A small magnet is suspended by a silk thread from a rigid support such that the magnet can freely swing. How will it rest? Draw a diagram to show it.
Explain what do you understand by magnetic induction. What role does it play in attraction of a piece of iron by a magnet?
A small iron bar is kept near the north pole of a bar magnet. How does the iron bar acquire magnetism? Draw a diagram to show the polarity on the iron bar. What will happen if the magnet is removed?