TNPSC Physics Heat and Temperature Quiz 5

TNPSC Physics Heat and Temperature Quiz 5 – Detailed Explanations

This TNPSC Physics Heat and Temperature Quiz 5 concept booster explains the key ideas behind each question, focusing on important areas like heat flow, thermal expansion, evaporation, latent heat, and heat transfer methods. These are commonly asked topics where students often make mistakes in TNPSC exams.

By going through this physics heat and temperature quiz concept booster, you will clearly understand the concepts with simple explanations and real-life examples, helping you answer similar TNPSC physics heat and temperature MCQ questions with confidence.

Q1. Which of the following determines the direction of heat flow between two bodies?

Heat always flows from a body at higher temperature to a body at lower temperature. The direction of heat transfer depends only on the temperature difference, not on mass or volume.

Key Points:
• Heat flows from hot → cold
• Depends on temperature difference
• Independent of mass and volume
• Basic principle of thermodynamics

Real-life Example:
A hot cup of tea cools down because heat flows to the surrounding air.

Answer: Temperature difference

---

Q2. A metal lid becomes loose when heated because:

When a metal lid is heated, it expands due to thermal expansion. This increases its size slightly, making it easier to open.

Key Points:
• Heating causes expansion
• Metals expand on heating
• Size increases slightly
• Helps in loosening tight lids

Real-life Example:
Running hot water over a tight jar lid helps to open it easily.

Answer: It expands

---

Q3. Which of the following substances has the highest heat capacity?

Water has a very high specific heat capacity, meaning it can absorb a large amount of heat without a significant rise in temperature.

Key Points:
• Water has high heat capacity
• Absorbs more heat
• Temperature changes slowly
• Important in climate control

Real-life Example:
Coastal areas have moderate temperatures because water heats and cools slowly.

Answer: Water

---

Q4. Why does a wet cloth dry faster on a hot day?

Higher temperature increases the rate of evaporation. More heat energy allows water molecules to escape into the air quickly.

Key Points:
• High temperature → faster evaporation
• Molecules gain more energy
• Increases drying speed
• Common in summer

Real-life Example:
Clothes dry faster under sunlight than in shade.

Answer: Faster evaporation

---

Q5. Which of the following is used to measure humidity?

A hygrometer is used to measure the amount of moisture present in the air, known as humidity.

Key Points:
• Hygrometer measures humidity
• Used in weather studies
• Indicates moisture level
• Important for climate analysis

Real-life Example:
Weather reports use hygrometers to measure humidity levels.

Answer: Hygrometer

---

Q6. Which of the following changes state from gas to liquid?

The process in which a gas changes into a liquid is called condensation. This happens when the gas loses heat and its particles come closer together.

Key Points:
• Gas → liquid = condensation
• Occurs on cooling
• Heat is released
• Opposite of evaporation

Real-life Example:
Water droplets form on the outside of a cold bottle due to condensation.

Answer: Condensation

---

Q7. Why do black surfaces get hotter in sunlight?

Black surfaces absorb more heat radiation compared to lighter surfaces. This is why they become hotter when exposed to sunlight.

Key Points:
• Black absorbs more heat
• Less reflection
• Higher temperature gain
• Important in heat absorption

Real-life Example:
Wearing black clothes in summer feels hotter than wearing white clothes.

Answer: They absorb more heat

---

Q8. Which of the following is an example of good heat insulation?

A woolen blanket is a good insulator because it traps air, and air is a poor conductor of heat, reducing heat loss.

Key Points:
• Wool traps air
• Air is poor conductor
• Reduces heat transfer
• Used in winter

Real-life Example:
We use woolen clothes to stay warm in cold weather.

Answer: Woolen blanket

---

Q9. When a gas is cooled, its volume generally:

Cooling a gas reduces the kinetic energy of its particles. They move closer together, resulting in a decrease in volume.

Key Points:
• Cooling reduces energy
• Particles come closer
• Volume decreases
• Related to gas laws

Real-life Example:
Air in a balloon shrinks when kept in a cold environment.

Answer: Decreases

---

Q10. Which of the following is used to detect heat radiation?

A thermopile is used to detect and measure heat radiation by converting thermal energy into electrical energy.

Key Points:
• Detects heat radiation
• Converts heat to electricity
• Sensitive instrument
• Used in experiments

Real-life Example:
Used in scientific devices to measure infrared radiation.

Answer: Thermopile

---

Q11. Why does steam cause more burns than boiling water?

Steam contains latent heat of vaporization. When it condenses on the skin, it releases this extra heat, causing more severe burns.

Key Points:
• Steam has latent heat
• Releases extra heat on condensation
• Causes severe burns
• More dangerous than hot water

Real-life Example:
Steam from a cooker can cause worse burns than boiling water.

Answer: It contains latent heat

---

Q12. Which of the following is an example of latent heat?

Latent heat is involved when a substance changes its state without changing temperature. Melting ice is a common example.

Key Points:
• No temperature change
• State change occurs
• Heat absorbed or released
• Important concept

Real-life Example:
Ice melts into water without increasing temperature initially.

Answer: Melting ice

---

Q13. Which of the following materials expands more on heating?

Different materials expand at different rates. Aluminium expands more than iron or copper due to its higher coefficient of thermal expansion.

Key Points:
• Aluminium expands more
• High expansion rate
• Depends on material
• Important in engineering

Real-life Example:
Aluminium structures expand more in hot weather.

Answer: Aluminium

---

Q14. Why are double-walled vessels used to store hot liquids?

Double-walled vessels reduce heat transfer by minimizing conduction and convection, helping to keep liquids hot for a longer time.

Key Points:
• Reduces heat loss
• Minimizes conduction & convection
• Maintains temperature
• Used in thermos flasks

Real-life Example:
Thermos bottles keep tea hot for hours.

Answer: To reduce heat transfer

---

Q15. When temperature increases, viscosity of liquids generally:

As temperature increases, the intermolecular forces in liquids decrease, allowing them to flow more easily, which reduces viscosity.

Key Points:
• Temperature ↑ → viscosity ↓
• Liquids flow easily
• Reduced internal resistance
• Opposite in gases

Real-life Example:
Oil flows faster when heated.

Answer: Decreases

---

Q16. Which of the following is used in solar cookers?

Solar cookers use reflection to concentrate sunlight onto a point, increasing temperature and cooking food.

Key Points:
• Uses reflection
• Concentrates sunlight
• Produces heat
• Eco-friendly method

Real-life Example:
Mirrors in solar cookers focus sunlight to cook food.

Answer: Reflection

---

Q17. Why does a glass tumbler crack when hot water is poured suddenly?

When hot water is poured suddenly, the inner surface expands faster than the outer surface, causing uneven expansion and leading to cracks.

Key Points:
• Uneven expansion
• Inner surface heats first
• Causes stress
• Leads to cracking

Real-life Example:
Glass may break if hot water is poured quickly.

Answer: Uneven expansion

---

Q18. Which of the following is the coldest temperature?

−273°C is absolute zero, the lowest possible temperature where molecular motion is minimal.

Key Points:
• Absolute zero
• Lowest temperature
• Minimal molecular motion
• 0 Kelvin

Real-life Example:
Used as a reference point in thermodynamics.

Answer: −273°C

---

Q19. Which factor affects the rate of evaporation?

Evaporation depends on multiple factors such as temperature, surface area, and wind speed. All these increase the rate of evaporation.

Key Points:
• Temperature ↑ → faster evaporation
• Larger surface area → faster
• Wind speed increases rate
• Multiple factors involved

Real-life Example:
Clothes dry faster on a windy and sunny day.

Answer: All of these

---

Q20. Which of the following is an example of conduction in daily life?

Conduction is the transfer of heat through direct contact. Ironing clothes is an example where heat transfers from the hot iron to the fabric.

Key Points:
• Heat transfer by contact
• No movement of particles
• Occurs in solids
• Important mode of heat transfer

Real-life Example:
Iron transfers heat directly to clothes during ironing.

Answer: Ironing clothes

---

Final Revision Tips

• Heat always flows from higher temperature to lower temperature
👉 Direction depends only on temperature difference

• Thermal expansion is common in metals
👉 Heating → expansion → used in daily life (lid opening, railway tracks)

• Water has high specific heat capacity
👉 Heats slowly and cools slowly (important TNPSC concept)

• Evaporation increases with:
👉 Temperature ↑
👉 Surface area ↑
👉 Wind speed ↑

• Latent heat = heat without temperature change
👉 Example: Melting ice, steam burns

• Steam is more dangerous than boiling water
👉 Because it contains latent heat

• Black surfaces absorb more heat
👉 White surfaces reflect heat

• Insulators vs Conductors:
👉 Wool → good insulator
👉 Metals → good conductors

• Heat transfer methods:
👉 Conduction → direct contact (iron box)
👉 Convection → liquid/gas movement (boiling water)
👉 Radiation → no medium needed (sun heat)

• Gas behavior:
👉 Cooling → volume decreases
👉 Heating → expansion

• Absolute zero = −273°C (0 Kelvin)
👉 Lowest possible temperature

• Common instruments:
👉 Hygrometer → humidity
👉 Thermopile → heat radiation

🔗 Learn more:

For detailed practice and concept clarity, refer NCERT Exemplar problems on Heat:
👉 https://ncert.nic.in/pdf/publication/exemplarproblem/classVII/Science/geep104.pdf