Electricity travels at the speed of light, More than 1,86,000 miles per second.
As we all know that Energy can neither be created nor destroyed,
It can only be transformed from one form to another.
The same thing applies with the electrical engergy. To understand this better, let us observe certain electrical
appliances at home. You must have observed, fan getting heated up after running for certain interval of time.
It applies with all the electrical appliances. You must have also observed this phenomena with computer,
refrigerator, T.V set, electric heater, cloth iron, electric motor. etc.. the list goes on.
Now, the question arises why does it happen? And the anser is very simple. It is because of transformation
of electrical energy into heat energy. When the electric current folows through any electrical appliance.
some amount of electrical energy is hindered or obstructed by the appliance. And this happens due to Resistance
of the appliance. And this hindered electrical energy is given out in the form of heat.
This phenomena is called heating effect of electric current.
In the previous section, we have seen that how heat is released from electrical appliance.
You must have observed that some electrical appliance heats faster, while others slower.
By this we understand that there must be some factor which causes
different appliance to heat at different rates.
The Heat (H) produced depends on the following factors
(i) Current (I):
Heat is directly proportional to the square of current
H ∝ I2
(ii) Resistance (R):
Heat is directly proportional to the
Resistance of the appliance.
H ∝ R
(iii) Time (t):
Heat is directly proportional to the
time interval.
H ∝ t
From the above 3 factors we get the equations:
H ∝ I2 Rt H = I2 Rt
The heating effect of electric current has wide range of application. This techniques is used in
appliances like electric heater, electric iron, electric room heater, hair dryer, electric bulb etc.
All these appliances have a coil of wire called an element. when electric current flows through
the element, it becomes hot and gives out heat. The amount of heat produced in a wire depends upon
its material, length and thickness.
