Question

What is electromagnet and what is fuse? Define magnetic effect of current.

Answer 1

An electromagnet is a magnet that runs on electricity. Unlike a permanent magnet, the strength of an electromagnet can easily be changed by changing the amount of electric current that flows through it. The poles of an electromagnet can even be reversed by reversing the flow of electricity.
Use:

Whatever powered devices we use, from table clocks to microwave ovens, have some form of electromagnetic principle involved in their functioning. It is electromagnetism which has given the flexibility for switching of/on electricity as required
The magnetic effect of an electric current was discovered by Hans Christian Oersted in 182. To demonstrate the effect, a plotting compass is placed close to a long straight wire which is carrying current. A deflection is noted. By reversing the direction of the current, the compass needle will be deflected in the opposite sense.
Experiment to demonstrate the magnetic effect of an electric current
Apparatus : Accumulator or power supply unit, rheostat, ammeter, switch, connecting wires, stiff board, plotting compass, 20 cm of straight copper wire. The copper wire may be obtained from a waste piece of electrical cable.
Procedure

1. Set up the apparatus as shown, with the board suitably supported horizontally and the wire passing vertically through its centre.
2. Switch on and adjust the rheostat to give an ammeter reading of 4 A.
3. Place the compass at any point on the board and mark the position of the compass’s head and tail, having tapped it gently to ensure it is not sticking.
4. Move the compass and mark the new position of the head when the tail is directly over the previous position of the head.
5. Proceed in this fashion until a complete loop has been traversed. Join the dots using a pencil.
6. With the compass placed at different distances from the wire, complete other loops.