medium importancemedium difficulty5 min

Heating Effect

The heating effect of electric current is the production of heat when current passes through a conductor with resistance.

In one line: Current squared decides the heat.

Practice This Concept

Understand it

As charges move through a resistor, some electrical energy changes into heat. This is why appliances like electric irons, heaters, and fuses depend on the heating effect. The heat produced depends strongly on current, resistance, and time.

Example

An electric iron becomes hot because its coil has resistance and current passes through it.

Formula and rule

H = I²Rt, where H is heat produced, I is current, R is resistance, and t is time.

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

1If I = 2 A, R = 3 ohm, and t = 5 s, then H = I²Rt = 2² × 3 × 5 = 60 J.
2So the heat produced is 60 joule.

Method you can reuse

1Identify current, resistance, and time.
2Square the current value.
3Multiply by resistance and time.
4Write the final heat in joules.

Sketch it in your answer

Show a resistor coil or heating element in a circuit, with heat waves drawn near the element and current flowing through it.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

If current in the same wire is doubled and other factors stay the same, how does heat change?

Think first, then show answer

The heat becomes four times because heating is proportional to the square of current, so doubling current gives 2 squared times heat.

Common wrong answer

A common wrong answer is to think heat is directly proportional only to time. That ignores the important square of current.

Don't mix this up

Students often think heating depends only on time and forget the strong effect of current.

Exam tip

Use the square of current carefully in numericals because it changes the answer fast.

Write it in the exam

Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.

How CBSE asks it

Frequently asked in numericals, fuse-related questions, and application questions about electric appliances.

1
Enough for 1 mark
The heating effect of electric current is the production of heat when current passes through a conductor with resistance.
2
Add for 2 marks
Example: An electric iron becomes hot because its coil has resistance and current passes through it.
3
Add for 3 marks
As charges move through a resistor, some electrical energy changes into heat.

MCQ Quiz

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