Read the following passage and answer the questions that follow : Swati, a class 10 student, observes that when she passes close to the refrigerator in her kitchen, she feels the heat, although the things kept inside the refrigerator are cool. (a) Describe the cause of heating in the above-mentioned case. (b) A current I flows through a resistor of resistance R when the potential difference across it is V. Applying Ohm’s law, write the formula for amount of heat produced by the resistor in time t. (c)(i) Write any two practical applications of heating effect of electric current. (c)(ii) Define the commercial unit of electric energy and express it in Joules (J).

(a) Heating effect of current – part of the electrical energy is lost as heat; (b) H = I²Rt; (c)(i) electric heater, electric iron (also fuse, toaster); (c)(ii) 1 kWh = energy used by 1 kW in 1 h = 3.6 × 10^6 J

ScienceCBSE Class 10 · Board exam 2026, set 31/2/1 · 4 marks · Case-based

CBSE Class 10 Science 2026: question 38

Set in the CBSE Class 10 board exam of 2026, paper 31/2/1, section C, question 38, for 4 marks. Try it first; the hints and our step-by-step solution are below.

Q38 · 4 marks · Case-basedCompetency-basedElectricity

Read the following passage and answer the questions that follow :

Swati, a class 10 student, observes that when she passes close to the refrigerator in her kitchen, she feels the heat, although the things kept inside the refrigerator are cool.

(a)
Describe the cause of heating in the above-mentioned case.
1 mark
(b)
A current $I$ flows through a resistor of resistance $R$ when the potential difference across it is $V$ . Applying Ohm’s law, write the formula for amount of heat produced by the resistor in time $t$ .
1 mark
(c)(i)
Write any two practical applications of heating effect of electric current.
2 marks
OR
(c)(ii)
Define the commercial unit of electric energy and express it in Joules (J).
2 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 31/2/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Does all the electrical energy supplied to an appliance get used for its job?

Hint 2

Start from $W = V I t$ and replace $V$ using Ohm's law.

Hint 3

For kWh, convert 1 kW to W and 1 h to seconds and multiply.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

(a) The refrigerator's compressor and circuits carry electric current. Only part of the electrical energy does useful work (cooling); the rest is turned into heat because of the resistance of the wires and coils (heating effect of current). This heat is given out at the back and sides, so Swati feels it.
1 mark
(b) Work done in time $t$ : $W = V Q = V I t$ . By Ohm's law $V = I R$ , so the heat produced is $H = I^{2} R t$ (equivalently $H = \frac{V ^{2}}{R} t$ ).
1 mark
(c)(i) Applications of the heating effect of current: (1) electric heater / electric iron / toaster / oven; (2) electric fuse (melts on excess current) / filament of electric bulb.
2 marks
(c)(ii) The commercial unit of electric energy is the kilowatt-hour (kWh): the energy used when an appliance of power 1 kW runs for 1 hour.
$1 kWh = 1000 W \times 3600 s = 3.6 \times 1 0^{6}$ J
2 marks

Answer: (a) Heating effect of current – part of the electrical energy is lost as heat; (b) $H = I^{2} R t$ ; (c)(i) electric heater, electric iron (also fuse, toaster); (c)(ii) 1 kWh = energy used by 1 kW in 1 h = $3.6 \times 1 0^{6}$ J

Where the marks are

(a) Part of electric energy converted into heat due to resistance (1 mark)
(b) $H = I^{2} R t$ derived using $V = I R$ (1 mark)
(c)(i) Any two correct applications (1 + 1 marks)
(c)(ii) Definition of kWh (1 mark) and $1 kWh = 3.6 \times 1 0^{6}$ J (1 mark)

Revise the chapter

Chapter: Electricity (notes, formulas, where marks are lost and every past question)
Topic: Heating Effect of Electric Current

Practise this chapterBoard-style questions from Electricity, one at a time, marked against the answer key and marking points.Back to the full paper2026 board paper, set 31/2/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.

CBSE Class 10 Science 2026: question 38

Hints

Step-by-step solution

Revise the chapter

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