(i) Aim: How electric fuse works?
Apparatus required : Two nails, card board, very thin aluminium strip, a 12 V battery, key and connecting wires.
Procedure:
Insert the two nails vertically on the card board. Take very thin aluminium strip and tie it between the nails. Make a circuit as shown in figure with 12 V battery and key with the help of connecting wires.
If there are any fans running in the room, switch them off. Now switch on the current in the circuit by pressing the key or by moving the switch of the ‘ON’ position. Now pass the current through the circuit for some time. Observe the strand of aluminium strip between the two nails carefully. Observation: The strand of aluminum strip melt and break quickly on passing the large electric current through it.
Conclusion: When current flows through the circuit, exceed the rating of aluminium strip, i.e. safe limit, its temperature increases. This make it overheated. As a result, aluminium strip melts and breaks the circuit. Hence, very thin aluminium strip between the two nails acts as a fuse wire. This activity shows that how fuse works
(ii) Significance of insulation colour:
Red colour insulation wire – Live wire
Black colour insulation wire – Neutral wire
Green colour insulation wire – Earth wire
Live wire is at higher potential of 220 V while neutral wire is at zero potential. So, potential difference between red and black insulation wire is 220 V.
