Energy can neither be created nor destroyed but can only be converted from one form to another.
According to the law of conservation of energy, the total energy in a system is always constant.
When an electric current is passed through a high resistance wire, like nichrome wire, the resistance wire becomes very hot and produces heat.
Electric current is converted partially to useful work and partially to heat energy. This is known as the heating effect of electric current or joule heating or ohmic heating or resistive heating.
EQUATION: HEATING EFFECT OF CURRENT
JOULE’S LAW OF HEATING:
According to joule’s low of heating given by the formula
The heat produced in a wire is directly proportional to:
Resistance of wire (R)
Time (t), for which current is passed
APPLICATIONS OF THE HEATING EFFECT OF CURRENT
Electrical Heating Appliances: The heating effect of current is utilised in the working of electrical heating appliances such as electric iron, electric kettle, electric toaster, electric oven, room heaters, water heaters (geysers), etc.
Electric Iron: In electric iron, bimetallic plates are used to break the flow of current when temperature reaches a certain value. This is indicated by glowing of a red light in an iron box.
Electric Heater: In electric heater, circuit breaker is used instead of bimetallic plates.
Electric bulbs: The heating effect of electric current is utilised in electric bulbs (electric lamps) for illumination. When electric current passes through a very thin, high resistance tungsten filament of an electric bulb, the filament becomes white-hot and emits light.
Electric Fuse: The heating effect of electric current is utilised in electric fuse for protecting household wiring and electrical appliances. A fuse is a short length of a thin tinplated copper or zinc wire having low melting point. The thin fuse wire has a lower resistance than the rest of the electric wiring in a house. So, when the current in a household electric circuit rises too much due to some reason, then the fuse wire gets heated too much, melts and breaks the circuit (due to which the current stops flowing). This prevents the fire in house.