If the electrical circuit is purely resistive, that is a configuration of resistors only connected to battery, the source energy continually gets dissipated in the form of heat. This is known as Joule’s heating effect of electric current. Joule’s law of heating is given by the relation:
H= I2Rt. The law implies that : heat produced in a resistor is
(i) Directly proportional to the square of current for a given resistance
(ii) Directly proportional to the resistance of given circuit.
(iii) Directly proportional to the time for which the resistance flows through the resistor.
It can be demonstrated experimentally by following:
When an electric field is applied across the ends of a conductor, the free electrons starts moving towards the electric field. These electrons suffers collision with the atoms which have lost electrons. Due to the collision, energy is transferred to the atoms and they vibrate as they gain energy due to which heat is developed in the conductor. The more is the current, the more will be heat. This is Joule’s heating effect.
An electric fuse is wire which is made of a material of high resistance and low melting point. Using an electric fuse prevents the flow of unduly high electric current and protects the appliances from the damage. Due to Joule heating, the fuse melts to break the electric circuit.
The four applications in daily life are:
1. In electrical heaters.
2. In electrical iron
3. In electrical fuse wire
4. In electrical bulb
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