Question

Differentiate between bar magnet and an electromagnet.

Answer 1

Hint: A bar magnet is a permanent magnet that has its own magnetic field and an electromagnet is a temporary magnet that produces a magnetic field in presence of electric current from a source.

Complete answer:
Bar magnets: These are made of naturally occurring minerals called magnetite. These magnets can attract any ferromagnetic material (e.g.- iron) and are permanently magnetised. Their magnetic field cannot be turned on or off. Their magnetic field strength cannot be varied, they are weak magnets and their strength usually decreases with time. They have fixed poles and their magnetic field lines are from the north pole and point towards the south pole. Their polarity cannot be reversed.

Electromagnets: They are man-made magnets. When a current carrying wire is wrapped around a piece of iron the current produces a magnetic field around the wire and the iron piece becomes magnetized. These magnets are temporary magnets and their magnetic field can be turned on or off when current supply is turned on or off. Their magnetic strength can also be varied according to the need and they can produce very strong magnetic fields. Their poles are not fixed so their polarity can also be changed from north pole to south pole or vice versa by changing the direction of flow of current.

Additional Information:
A solenoid is an example of an electromagnet whose magnetic strength can be varied by increasing or decreasing the number of turns of the current carrying coil.

Note:
Bar magnets are used in making credit and debit cards, magnetic needles or compass or in laboratory experiments and electromagnets are used in manufacture of telephones, loud speakers, stereos etc.