Test your knowledge with this Physics Heat and Temperature quiz created especially for TNPSC preparation. The questions cover important TNPSC Science Heat and Temperature topics frequently asked in competitive exams. Attempt this TNPSC Physics Heat and Temperature free Online Quiz to evaluate your preparation, improve conceptual clarity, and gain confidence before the actual examination.
TNPSC Heat and Temperature Questions Detailed Explanations
Every question in this Physics Heat and Temperature quiz is followed by a clear explanation to help you understand the scientific concepts behind the correct answer. Reviewing these explanations will strengthen your knowledge of TNPSC Science Heat and Temperature topics and improve your performance in future exams.
1. What is the SI unit of temperature?
✅ Correct Answer: B. Kelvin
Explanation: Kelvin (K) is the SI unit of thermodynamic temperature. It is an absolute temperature scale that begins at absolute zero (0 K), the lowest possible temperature where the thermal motion of particles is at its minimum. Unlike the Celsius scale, Kelvin does not use the degree symbol (°).
In scientific research and physics calculations, Kelvin is preferred because many physical laws, such as the gas laws, require absolute temperature.
Key Points:
- SI unit of temperature: Kelvin (K)
- 0 K = −273.15°C (Absolute Zero)
- 273 K = 0°C
- Water freezes at 273 K and boils at 373 K
TNPSC Tip:
Remember that Kelvin never uses the degree (°) symbol.
2. The boiling point of water at standard atmospheric pressure is:
✅ Correct Answer: C. 100°C
Explanation: Pure water boils at 100°C (373 K) when the atmospheric pressure is 1 atmosphere (1 atm or 760 mm Hg). At this temperature, water changes from the liquid state to the gaseous state.
The boiling point changes with atmospheric pressure. At high altitudes, where air pressure is lower, water boils below 100°C. In pressure cookers, the pressure is increased, raising the boiling point and allowing food to cook faster.
Key Points:
- Boiling point of water = 100°C
- Standard pressure = 1 atm
- Boiling point decreases at high altitudes
- Boiling point increases with pressure
Real-Life Example:
A pressure cooker cooks food faster because water boils above 100°C inside it.
3. Which instrument is used to measure temperature?
✅ Correct Answer: B. Thermometer
Explanation: A thermometer is an instrument used to measure the temperature of solids, liquids, gases, and the human body. It works by using materials whose physical properties change with temperature, such as the expansion of mercury or alcohol.
Modern thermometers include digital, infrared, and electronic thermometers.
Key Points:
- Measures temperature accurately
- Clinical thermometer → Human body
- Laboratory thermometer → Experiments
- Digital thermometer → Fast and safe measurement
TNPSC Tip:
Do not confuse a thermometer (temperature) with a barometer (pressure).
4. Heat is a form of:
✅ Correct Answer: A. Energy
Explanation: Heat is a form of energy that flows naturally from a body at higher temperature to another at lower temperature due to the temperature difference. Heat is not a substance or matter but energy in transit.
Once transferred, heat can increase temperature, cause expansion, or change the state of matter.
Key Points:
- Heat is energy in transit
- Flows from hot body to cold body
- SI unit of heat = Joule (J)
Real-Life Example:
A hot cup of tea loses heat to the surrounding air until both reach the same temperature.
5. Transfer of heat through direct contact is called:
✅ Correct Answer: A. Conduction
Explanation: Conduction is the transfer of heat through direct contact between particles without the movement of the material itself. It mainly occurs in solids because their particles are closely packed.
Metals are good conductors due to the presence of free electrons that transfer heat quickly.
Key Points:
- Occurs mainly in solids
- Requires physical contact
- No movement of the substance
Real-Life Example:
A metal spoon becomes hot when left in a cup of hot tea.
6. Heat transfer in liquids and gases mainly occurs by:
✅ Correct Answer: C. Convection
Explanation: Convection is the transfer of heat through the movement of liquids and gases. When a fluid is heated, it expands, becomes less dense, and rises. Cooler, denser fluid sinks, forming convection currents.
These currents continuously transfer heat throughout the fluid.
Key Points:
- Occurs only in liquids and gases
- Heat transfer by movement of fluid
- Forms convection currents
Real-Life Example:
Sea breeze and land breeze occur because of convection currents.
7. The temperature at which water freezes is:
✅ Correct Answer: A. 0°C
Explanation: Pure water freezes at 0°C (273 K) under standard atmospheric pressure. At this temperature, water changes from the liquid state to solid ice.
The freezing point is one of the fixed reference points used to define the Celsius scale.
Key Points:
- Freezing point = 0°C
- Equivalent to 273 K
- Used as lower fixed point of Celsius scale
TNPSC Tip:
Water freezes at 0°C and boils at 100°C under normal atmospheric pressure.
8. Which scale does not use negative values?
✅ Correct Answer: C. Kelvin
Explanation: The Kelvin scale begins at absolute zero (0 K), the lowest theoretically possible temperature. Since temperatures cannot be lower than absolute zero, Kelvin values are never negative.
This makes Kelvin the standard scale for scientific calculations.
Key Points:
- Lowest value = 0 K
- No negative temperatures
- SI temperature scale
Memory Trick:
Kelvin = Keeps everything positive.
9. The device used to measure atmospheric pressure is:
✅ Correct Answer: B. Barometer
Explanation: A barometer measures atmospheric pressure. Atmospheric pressure changes with altitude and weather conditions.
Two common types are:
- Mercury barometer
- Aneroid barometer
Meteorologists use barometers to help forecast weather.
Key Points:
- Measures atmospheric pressure
- Used in weather forecasting
- Unit often expressed in mm Hg or Pascal (Pa)
TNPSC Tip:
Thermometer → Temperature
Barometer → Pressure
10. The normal human body temperature is:
✅ Correct Answer: C. 37°C
Explanation: The average normal human body temperature is 37°C (98.6°F). However, slight variations are normal depending on age, physical activity, and the time of day.
A temperature above 37°C may indicate fever.
Key Points:
- Normal body temperature = 37°C
- Equivalent to 98.6°F
- Measured using a clinical thermometer
Real-Life Example:
Doctors use digital or clinical thermometers to check body temperature.
11. Heat from the Sun reaches Earth mainly by:
✅ Correct Answer: C. Radiation
Explanation: Heat from the Sun reaches Earth through radiation, which transfers energy using electromagnetic waves. Radiation does not require any material medium, allowing heat to travel through the vacuum of space.
Key Points:
- No medium required
- Travels through vacuum
- Fastest mode of heat transfer
Real-Life Example:
You feel sunlight warming your skin even though space between the Sun and Earth is nearly a vacuum.
12. Which metal is a good conductor of heat?
✅ Correct Answer: C. Copper
Explanation: Copper is an excellent conductor of heat because it contains many free electrons that transfer thermal energy efficiently. It is widely used in electrical wiring, cooking utensils, and heat exchangers.
Key Points:
- Excellent conductor of heat
- Also conducts electricity well
- Used in household wiring and cookware
TNPSC Tip:
Silver conducts heat better than copper but is too expensive for common use.
13. Expansion of substances due to heat is called:
✅ Correct Answer: B. Thermal Expansion
Explanation: When substances are heated, their particles gain kinetic energy and move farther apart. This causes an increase in length, area, or volume, known as thermal expansion.
Most solids, liquids, and gases expand when heated.
Key Points:
- Heating causes expansion
- Cooling causes contraction
- Used in engineering design
Real-Life Example:
Railway tracks have expansion gaps to prevent bending during hot weather.
14. Which of the following is a poor conductor of heat?
✅ Correct Answer: C. Wood
Explanation: Wood is a poor conductor (insulator) of heat because it does not allow heat to pass through easily. This makes it useful for handles of cooking utensils.
Key Points:
- Wood is an insulator
- Prevents heat transfer
- Safe to handle hot objects
Real-Life Example:
Cooking pans often have wooden handles to protect hands from heat.
15. The SI unit of heat energy is:
✅ Correct Answer: B. Joule
Explanation: Heat is a form of energy, and the SI unit of all forms of energy is the Joule (J). Although calories are sometimes used, scientific measurements use Joules.
Key Points:
- SI unit = Joule (J)
- 1 calorie ≈ 4.186 Joules
- Used in physics calculations
TNPSC Tip:
Do not confuse Joule (energy) with Watt (power).
16. Which color absorbs more heat?
✅ Correct Answer: B. Black
Explanation: Black surfaces absorb nearly all the heat and radiation that falls on them, whereas white and shiny surfaces reflect most of the heat. This property is important in clothing, buildings, and solar energy applications.
Key Points:
- Black → Best absorber
- White → Best reflector
- Dark colours become hotter faster
Real-Life Example:
People prefer light-coloured clothes during summer because they reflect sunlight.
17. The process of conversion of liquid into gas is called:
✅ Correct Answer: B. Evaporation
Explanation: Evaporation is the process by which liquid molecules at the surface gain enough energy to escape into the gaseous state. It can occur at any temperature below the boiling point.
Evaporation causes cooling because high-energy molecules leave the liquid.
Key Points:
- Surface phenomenon
- Occurs at any temperature
- Produces cooling effect
Real-Life Example:
Sweat evaporates from the skin and cools the body.
18. Which thermometer is commonly used in laboratories?
✅ Correct Answer: B. Laboratory thermometer
Explanation: A laboratory thermometer is designed to measure temperatures during scientific experiments. It generally measures temperatures from −10°C to 110°C and does not have the constriction found in clinical thermometers.
Key Points:
- Used in laboratories
- Range: approximately −10°C to 110°C
- Suitable for liquids and experiments
TNPSC Tip:
Clinical thermometer → Human body
Laboratory thermometer → Scientific experiments
19. Which process involves heat transfer without any medium?
✅ Correct Answer: C. Radiation
Explanation: Radiation transfers heat through electromagnetic waves and does not require a material medium. Therefore, it is the only mode of heat transfer that works through a vacuum.
Key Points:
- No medium needed
- Travels through vacuum
- Electromagnetic waves carry heat
Real-Life Example:
The warmth you receive from a fire without touching it is due to radiation.
20. The expansion of mercury in a thermometer is an example of:
✅ Correct Answer: B. Thermal Expansion
Explanation: Mercury expands when heated and contracts when cooled. This predictable thermal expansion causes the mercury level to rise or fall inside the narrow tube of a thermometer, allowing temperature to be measured accurately.
Key Points:
- Mercury expands on heating
- Contracts on cooling
- Used in traditional thermometers
TNPSC Tip:
Thermometers work based on the principle of thermal expansion of liquids.
Quick Revision
- Heat is a form of energy, whereas temperature indicates how hot or cold a body is.
- The SI unit of temperature is Kelvin (K), while heat is measured in Joules (J).
- Heat always flows naturally from a hotter object to a colder object until thermal equilibrium is reached.
- Conduction mainly occurs in solids, convection in liquids and gases, and radiation can travel through a vacuum.
- Water freezes at 0°C (273 K) and boils at 100°C (373 K) under normal atmospheric pressure.
- Copper is a good conductor of heat, whereas wood, plastic, and rubber are poor conductors.
- Most substances expand on heating and contract on cooling, a phenomenon known as thermal expansion.
- Black surfaces absorb more heat, while light-coloured or white surfaces reflect more heat.
- A clinical thermometer is used to measure human body temperature, whereas a laboratory thermometer is used for scientific experiments.
- Remember the basic instruments: Thermometer → Temperature, Barometer → Atmospheric Pressure.
Further Reading
Build a stronger understanding of Heat and Temperature by exploring the official NCERT Class 7 Science – Chapter 3: Heat. This chapter explains the concepts of heat, temperature, thermometers, conduction, convection, radiation, and thermal expansion with simple examples, making it an excellent resource for strengthening your TNPSC Physics and General Science fundamentals.
Each question in this “Physics Heat and Temperature” quiz is accompanied by a detailed explanation to help you understand the correct answer and the science behind it. These exam-focused explanations cover important TNPSC Science Heat and Temperature concepts and reinforce frequently asked in TNPSC Physics Questions. Review them carefully to strengthen your knowledge, improve conceptual clarity, and prepare more effectively with this Online Quiz for the TNPSC General Science section.