Explain heating and lighting effect of electric current with help of an activity. Class 7

Dear Student,
The heating effect of current is defined by Joules Law of heating. It states that the heat 'H' produced by a resistor of resistance 'R' due to current 'I' flowing through it for time 't' is:

H = i 2 Rt

In a conductor when an electric field is applied across its ends, the free electrons available in it start drifting along the electric field. These electrons collide with the atoms which have lost the electrons. As a result of these collisions, some energy of the electrons is transferred to the atoms which vibrate violently as they gain energy. Thus, heat is developed in the conductor.

Greater the current, the greater will be the rate of collision and so greater will be the heat produced.

Some appliances using the heating effect of current

1 Room heater

2. Electric bulb

3. Electric Iron

4. Electric fuse

An activity can be done in the manner given below :
Take a resistor/ a metal conductor and let a large amount of electric current flow through it for some time. In some time, you would observe, that the metal conductor/ resistor have become hot. 
Also, the tungsten filament used in bulbs produces light due to the heat generated due to its high resistance.

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