What is Joule’s heating effect? How can it be demonstrated experimentally? List its four applications in daily life.
The Joule’s Law of Heating states that the heat produced in a resistor is:
(a) Directly proportional to the square of current for a given resistor.
(b) Directly proportional to resistance for a given current, and
(c) Directly proportional to the time for which the current flows through the resistor.
This can be expressed by following equation:
H =I2Rt
Here; I is electric current, R is resistance, t is time and H is heating effect.
Experiment to Demonstrate Joule’s Law of Heating:
• In this experiment, we will show the effect of current on heating.
• Take a water heating immersion rod and connect to a socket which is connected to regulator. It is important to recall that a regulator controls the amount of current flowing through a device.
• Keep the pointer of regulator on minimum and count the time taken by immersion rod to heat a certain amount of water.
• Increase the pointer of regulator to next level. Count the time taken by immersion rod to heat the same amount of water.
• Repeat above step for higher levels on regulator to count the time.
Observation: It is seen that with increased amount of electric current, less time is required to heat the same amount of water. This shows Joule’s Law of Heating.
Application: Electric toaster, oven, electric kettle and electric heater etc. work on the basis of heating effect of current.
