- Books Name
- CBSE Class 7 Science Book
- Param Publication
- CBSE Class 7
When the current carrying coil is brought near a suspended bar magnet one side of the coil repels the north pole of the magnet. The otherside of the coil attract the north pole of the magnet. Thus, a current carrying coil has both north and a south pole like a magnet. Such a magnet is called electromagnet.
The electromagnet can be made very strong and can lift very heavy loads. The electromagnets are also used to separate magnetic material from the junk. Doctors use tiny electromagnets to take out small pieces of magnetic material that have fallen in the eye. The most common use of electromagnet is electrical bell.
Factors which effect the strength of electromagnet :
(A) magnetic effect of current depends on number of turns.
(B) magnetic effect of current depends on the value of current.
(C) magnetic effect of current depends on the nature of core inside the coil.
8. To make an electromagnet.
• Take an iron nail of about 6-10 cm in length and wind an insulated copper wire on it
• Now connect the ends of the copper wire to the two terminals of a dry cell via a switch.
• Switch on the current through the circuit and bring a few iron pins near the wounded nail.
• Now switch off the current and see what happens.
The iron nail behaves like a magnet as long as current flows through the circuit. The pins cling to the nail when the switch is 'on' while they drop as soon as the switch disconnects the electric circuit. You can see an enhanced magnetic field (more pins cling to the nail) if you use a battery in place of a cell.