Heating Effect of Electric Current

When electric current is passed through a conductor, heat is generated in the conductor. This effect of electric current is known as heating effect of electric current.

In practice, when electric current is passed through the element of an electric heater, the element of the heater becomes red hot, because the electrical energy is converted into the heat energy. This is called heating effect of electric current and is used in manufacturing of many heating appliances like electric iron, electric kettle etc.

Cause of Heating Effect of Electric Current

When a potential difference is applied across the ends of a conductor, the free electrons moves with drift velocity and thus constitute the electric current in the conductor. The moving free electrons in the conductor collide with positive ions of the conductor.

On collision, the kinetic energy of free electrons being transferred to the ions with which they have collided. As a result of it, the kinetic energy of vibrations of the positive ions increases and hence the temperature of the conductor increases. Since the source of emf maintaining current in the conductor. Therefore, the electrical energy supplied by the source is converted into heat energy in the conductor.

Heat Produced in a Conductor by Electric Current

An English physicist James Prescott Joule found in his experiments that the amount of heat produced (H) when an electric current I amperes flows through a conductor of resistance R ohms for time t seconds is given by,

$$\mathrm{\mathit{H=I^{2}Rt}\: Joules}$$

This expression is known as Joule’s law of heating.

Therefore, according to Joule’s law of heating, the heat produced in a conductor is directly proportional to −

• Square of current through the conductor,
• Resistance of the conductor, and
• Time for which current being passed through the conductor.

Applications of Heating Effect of Electric Current

The heating effect of electric current is used in manufacturing of many heating appliances like electric heater, electric iron, electric bulb, electric kettle, soldering iron, electric toaster etc. Some of them are discussed as follows −

• Electric Heater − In electric heater, an electric current is passed through a high resistance (called heating element), thus producing the required heat. The heating element used is an alloy of nickel and chromium, called nichrome.

• Electric Bulb − Electric current is passed through the filament (made up tungsten) of the bulb due to which it being heating up to a certain temperature after which it is illuminated.

• Electric iron − In electric iron also, the current is passed through the heating element which is insulated from the iron box by mica. The heat produced in the element is transferred to the metallic part via mica.

• Electric Fuse − The heating effect of electric current also being used in manufacturing electric fuse for protecting electric circuits and devices. An electric fuse is a small piece of wire made up of thin tinplated copper or zinc having low melting point. When the electric current in an electric circuit increases too much due to some reason, the fuse wire gets heated too much, melt and break the circuit. Hence, protecting the electric circuit and appliances being damaged.