Heating Effect of Electric Current

When current flows through a conductor, heat energy is generated in the conductor due to its resistivity. This is called heating effect of electric current. The amount of heat produced is

• Directly proportional to the square of current flow on conductor
• Directly proportional to the resistance of conductor
• Directly proportional to the time for which current flow

If I is current, R is resistance ant t is time mentioned above then from the combination of above three conditions, amount of heat produced on conductor is

H = I² Rt

Use of heating effect of electric current

• Electric cookers- electric cookers turn red hot and the heat energy produced is absorbed by the cooking pot through conduction.
• Electric heaters- radiant heaters turn red at about 9000C and the radiation emitted is directed into the room by polished reflectors.
• Electric kettles- the heating element is placed at the bottom of the kettle so that the liquid being heated covers it. The heat is then absorbed by water and distributed throughout the whole liquid by convection.
• Electric irons- when current flows through the heating element, the heat energy developed is conducted to the heavy metal base raising its temperature. This energy is then used to press clothes. The temperature of the electric iron can be controlled using a thermostat (a bimetallic strip).

Q. Why nichrome is used as heating element?
Because of its low cost of manufacture, strength, ductility, resistance to oxidation, stability at high temperatures, and resistance to the flow of electrons, nichrome is widely used in electric heating elements in applications such as hair dryers, heaters and heat guns.