Question

State two advantages of an electromagnet over a permanent magnet.

Answer 1

Hint: An electromagnet is a temporary magnet generating magnetic field due to the current flowing through the wire wrapped around an iron core, whereas a permanent magnet generates a magnetic field by itself.

Complete step by step solution:
In an electromagnet, the magnetic field strength can be increased by increasing the number of turns of the current-carrying wire or by increasing the current in the wire. The magnetic field direction depends on the direction of the current. Magnetic field strength of a permanent cannot be changed.

An electromagnet generates a strong magnetic field but a permanent generates a weak magnetic field. The electromagnet‘s polarity can also be reversed by reversing the current direction. However, a permanent magnet’s poles are fixed.

Additional information:
Lodestone or magnetite is a permanent magnet which was used by mariners for navigation.
The Earth itself behaves as a huge permanent magnet with its magnetic south pole towards the geographic north and the magnetic north pole towards the geographic south. This is the reason why magnetic needles orient themselves in a north-south direction.

The magnetic domains in a permanent magnet remain aligned without any external field.
In 1820, Hans Oersted, a Danish physics teacher, hypothesized that electric current produces magnetic field and the direction of magnetic field depends on the direction of current.
In 1824, William Sturgeon invented the electromagnet, which was a horseshoe-shaped piece of iron warped with eighteen turns of copper wire.

Today electromagnets find a wide range of applications, such as MRI machines, motors, generators and magnetic separation equipment.

Note: An electromagnet requires a continuous current supply in order to produce a magnetic field. Its magnetization is lost when the current is stopped.