Practice tests · TNPSC

TNPSC physics practice questions: light, sound, heat and electricity

By the PrepMatic team · Updated 9 Oct 2026 · 3 min read

These four physics topics produce most of the everyday-science questions in the TNPSC General Studies paper, where General Science is Unit I and carries about 5 of the 75 questions. The questions rely on application: which mirror is used for what, why a material conducts, what a fuse does. The five questions below sample all four. More on the whole subject is in TNPSC General Science.

What this topic covers

• Light: reflection, refraction, mirrors and lenses, and the spectrum.
• Sound: how it travels, speed in different media, echo, and ultrasound.
• Heat: temperature scales and the three modes of heat transfer.
• Electricity and magnetism: Ohm's law, resistance, household wiring and safety devices.

Sample questions

Question 1

Which mirror is used as the rear-view mirror in vehicles?

• A. Plane mirror
• B. Concave mirror
• C. Convex mirror
• D. Cylindrical mirror

Question 2

Sound cannot travel through:

• A. a vacuum
• B. water
• C. steel
• D. air

Question 3

In liquids and gases, heat is transferred mainly by:

• A. reflection
• B. convection
• C. conduction
• D. radiation

Question 4

A resistor of 10 ohm carries a current of 2 A. The potential difference across it is:

• A. 0.2 V
• B. 5 V
• C. 12 V
• D. 20 V

Question 5

The domestic electric supply in India is alternating current with a frequency of:

• A. 50 Hz
• B. 25 Hz
• C. 60 Hz
• D. 100 Hz

Answers and explanations

1. C. A convex mirror always forms a small, upright image and covers a wide area, which is what a driver needs. A concave mirror would show an inverted image when the object is far.
2. A. Sound is a mechanical wave and needs a medium of particles. It travels through solids, liquids and gases but not through a vacuum.
3. B. In fluids, warm material becomes lighter and rises while cooler material sinks, setting up convection currents. Conduction dominates in solids, and radiation does not need a medium.
4. D. From Ohm's law, V = I × R = 2 × 10 = 20 V.
5. A. India uses alternating current at 50 Hz, with a household voltage of 230 V. Some countries, including the United States, use 60 Hz.

How to prepare these physics topics

Learn the applications table above as a set of one-line "this is used for that" facts. TNPSC prefers questions that connect a principle to something you see: the rear-view mirror, the safety fuse, the sound of thunder arriving after lightning (light is much faster than sound).

For electricity, remember the circuit basics: a voltmeter is connected in parallel, an ammeter in series, and the units are volt, ampere and ohm. Practise three or four Ohm's law calculations until the arithmetic is automatic, since a numerical question in this unit is almost always a single substitution.

For heat, convert between Celsius and Fahrenheit with F = C × 9/5 + 32, and remember that water boils at 100 degrees Celsius (373 kelvin) and freezes at 0 (273 kelvin). Normal human body temperature, 37 degrees Celsius, is 98.6 degrees Fahrenheit.

Spend less time on derivations, and no time at all on optics numericals involving lens formulas beyond the basics. If you need to widen your base, return to TNPSC physics: motion, force and energy practice.

Take the full topic test on PrepMatic

After revising the table, try a short science topic test on PrepMatic: about 15 questions in 30 minutes. When you have taken a few, your analytics show accuracy over time and speed per question, which indicates whether science deserves more of your week. You can also upload your own notes to generate a mock test from them, and the free Basic plan allows 2 uploaded documents.

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