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Electricity — Science STD 10 — Question

CBSE BoardEnglish MediumSTD 10ScienceElectricity5 Marks
Question
What is Joule’s heating effect? How can it be demonstrated experimentally? List its four applications in daily life.
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Answer

The Joule’s Law of Heating states that the heat produced in a resistor is:

  1. Directly proportional to the square of current for a given resistor.
  2. Directly proportional to resistance for a given current, and
  3. 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.

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