Below is a competitive-exam focused MCQ set based directly on the applications you listed, with emphasis on the type of “device/phenomenon → principle” questions commonly asked in General Science.
1. Sea breeze generally occurs during the day because:
(A) Sea heats faster than land
(B) Land heats faster than sea
(C) Both land and sea heat equally
(D) Sea has no atmospheric pressure
Answer: (B) Land heats faster than sea
Explanation: During the day, land becomes hotter more quickly than water. Warm air over land rises, and cooler air from the sea moves toward the land, producing a sea breeze.
2. The movement of air from the sea toward the land during the day is called:
(A) Land breeze
(B) Sea breeze
(C) Trade wind
(D) Monsoon wind
Answer: (B) Sea breeze
Explanation: Sea breeze is caused by differential heating of land and water and the resulting convection currents.
3. Land breeze generally occurs:
(A) During the daytime
(B) During the night
(C) Only during summer
(D) Only during winter
Answer: (B) During the night
Explanation: At night, land cools faster than water. Air above the relatively warmer sea rises, and cooler air from the land moves toward the sea.
4. The primary cause of both sea breeze and land breeze is:
(A) Radiation alone
(B) Differential heating of land and water
(C) Conduction alone
(D) Earth’s rotation alone
Answer: (B) Differential heating of land and water
5. Sea breeze and land breeze are mainly examples of heat transfer by:
(A) Conduction
(B) Convection
(C) Radiation
(D) Reflection
Answer: (B) Convection
6. A chimney helps smoke and hot gases escape from a building mainly because:
(A) Hot air is heavier than cold air
(B) Hot air rises due to convection
(C) Cold air rises rapidly
(D) Radiation pushes smoke upward
Answer: (B) Hot air rises due to convection
7. Chimneys are generally made tall because:
(A) Tall chimneys produce more heat
(B) They increase the upward movement of hot gases and improve ventilation
(C) They prevent convection
(D) They reduce atmospheric pressure to zero
Answer: (B) They increase the upward movement of hot gases and improve ventilation
8. Ventilators are generally provided near the ceiling of rooms because:
(A) Cold air always rises
(B) Hot air rises and accumulates near the ceiling
(C) Radiation cannot reach the ceiling
(D) Atmospheric pressure is highest there
Answer: (B) Hot air rises and accumulates near the ceiling
9. The circulation of air in a room due to warm air rising and cool air descending is an example of:
(A) Conduction
(B) Convection
(C) Radiation
(D) Evaporation
Answer: (B) Convection
10. Woollen clothes keep the body warm mainly because wool:
(A) Is a good conductor of heat
(B) Traps air, which is a poor conductor of heat
(C) Produces heat continuously
(D) Absorbs all radiation
Answer: (B) Traps air, which is a poor conductor of heat
11. Wool is suitable for winter clothing because it:
(A) Increases heat loss from the body
(B) Reduces heat transfer from the body to the surroundings
(C) Produces electrical energy
(D) Increases body temperature through radiation
Answer: (B) Reduces heat transfer from the body to the surroundings
12. A thermos flask is designed primarily to:
(A) Increase heat transfer
(B) Minimize heat transfer
(C) Increase evaporation
(D) Increase convection
Answer: (B) Minimize heat transfer
13. A vacuum between the double walls of a thermos flask primarily reduces:
(A) Radiation
(B) Conduction and convection
(C) Evaporation only
(D) Reflection
Answer: (B) Conduction and convection
14. The shiny or silvered surfaces inside a thermos flask help reduce heat transfer by:
(A) Conduction
(B) Convection
(C) Radiation
(D) Evaporation
Answer: (C) Radiation
15. A thermos flask reduces heat transfer by:
(A) Conduction only
(B) Convection only
(C) Radiation only
(D) Conduction, convection and radiation
Answer: (D) Conduction, convection and radiation
16. Black surfaces are generally:
(A) Good absorbers and good emitters of thermal radiation
(B) Poor absorbers of radiation
(C) Good reflectors but poor absorbers
(D) Unable to absorb heat
Answer: (A) Good absorbers and good emitters of thermal radiation
17. Black clothes are generally less comfortable in strong sunlight because black surfaces:
(A) Reflect most radiation
(B) Absorb more radiation
(C) Do not absorb radiation
(D) Produce cold air
Answer: (B) Absorb more radiation
18. White clothes are preferred in summer because they:
(A) Absorb more heat
(B) Reflect a greater proportion of thermal radiation
(C) Produce heat
(D) Increase evaporation only
Answer: (B) Reflect a greater proportion of thermal radiation
19. Why does food cook faster in a pressure cooker?
(A) Water evaporates at a lower temperature
(B) Increased pressure raises the boiling point of water
(C) Pressure decreases the temperature of water
(D) Food absorbs less heat
Answer: (B) Increased pressure raises the boiling point of water
20. In a pressure cooker, the boiling point of water:
(A) Decreases
(B) Increases
(C) Remains exactly 0°C
(D) Becomes equal to room temperature
Answer: (B) Increases
21. The main principle used in a pressure cooker is:
(A) Reduction of boiling point by pressure
(B) Increase of boiling point with increase in pressure
(C) Conversion of heat into electricity
(D) Cooling by evaporation
Answer: (B) Increase of boiling point with increase in pressure
22. A refrigerator transfers heat:
(A) From the cold interior to the warmer surroundings
(B) From the surroundings into the cold interior only
(C) From the freezer to space without energy input
(D) Without any energy consumption
Answer: (A) From the cold interior to the warmer surroundings
Explanation: A refrigerator uses external work to remove heat from its cold interior and reject it to the surroundings.
23. The back or sides of a refrigerator often feel warm because:
(A) The refrigerator produces cold air outside
(B) Heat removed from inside is released to the surroundings
(C) The refrigerator absorbs heat from the room
(D) No heat transfer occurs
Answer: (B) Heat removed from inside is released to the surroundings
24. A desert cooler cools air mainly through:
(A) Condensation
(B) Evaporation
(C) Freezing
(D) Radiation
Answer: (B) Evaporation
25. A desert cooler works more effectively on a:
(A) Humid day
(B) Dry day
(C) Rainy day
(D) Very cold day
Answer: (B) Dry day
Explanation: Evaporation is faster when the surrounding air has lower humidity.
26. A person feels cooler when sweating because:
(A) Sweat releases heat when it evaporates
(B) Evaporation of sweat removes heat from the body
(C) Sweat increases body temperature
(D) Sweat prevents heat loss
Answer: (B) Evaporation of sweat removes heat from the body
27. On a hot day, a person cools down mainly because:
(A) Sweat condenses on the skin
(B) Sweat evaporates and takes heat from the body
(C) Sweat increases radiation from the body
(D) Sweat increases atmospheric pressure
Answer: (B) Sweat evaporates and takes heat from the body
28. Water stored in an earthen pot becomes cool mainly because:
(A) Water freezes inside the pot
(B) Water evaporates through tiny pores in the pot
(C) Clay produces cold energy
(D) The pot absorbs sunlight
Answer: (B) Water evaporates through tiny pores in the pot
29. An earthen pot keeps water relatively cool because evaporation:
(A) Releases heat into the water
(B) Removes heat from the water
(C) Stops heat transfer
(D) Increases the boiling point
Answer: (B) Removes heat from the water
30. Ice wrapped in sawdust melts slowly because sawdust:
(A) Is a good conductor of heat
(B) Is a poor conductor of heat
(C) Produces ice
(D) Increases the temperature of ice
Answer: (B) Is a poor conductor of heat
31. Sawdust is used for insulating ice because it:
(A) Allows heat to flow rapidly
(B) Reduces the rate at which heat reaches the ice
(C) Increases the melting point of ice
(D) Produces cooling by radiation
Answer: (B) Reduces the rate at which heat reaches the ice
32. A metal spoon feels colder than a wooden spoon kept in the same room because:
(A) Metal has a lower temperature
(B) Metal conducts heat away from the hand faster
(C) Wood has a higher temperature
(D) Metal produces cold
Answer: (B) Metal conducts heat away from the hand faster
33. If a metal spoon and a wooden spoon are kept in the same room for a long time, their temperatures are:
(A) Necessarily different
(B) Approximately the same
(C) Metal’s temperature is always lower
(D) Wood’s temperature is always lower
Answer: (B) Approximately the same
Explanation: They reach thermal equilibrium with the surroundings. Metal merely feels colder because it conducts heat away from your hand more rapidly.
34. Gaps are left between railway tracks mainly to allow for:
(A) Contraction during winter only
(B) Thermal expansion during hot weather
(C) Increase in train speed
(D) Reduction of friction
Answer: (B) Thermal expansion during hot weather
35. If no gaps were provided between railway tracks, expansion during hot weather could cause:
(A) Tracks to become shorter
(B) Tracks to bend or buckle
(C) Trains to become lighter
(D) Friction to become zero
Answer: (B) Tracks to bend or buckle
36. Electric wires between poles are not stretched completely tight because:
(A) Electricity cannot flow through tight wires
(B) Wires contract in cold weather and may break if too tight
(C) Loose wires conduct electricity better
(D) Loose wires have no resistance
Answer: (B) Wires contract in cold weather and may break if too tight
37. The sag in overhead electric wires is mainly provided to accommodate:
(A) Magnetic expansion
(B) Thermal expansion and contraction
(C) Increase in electrical resistance only
(D) Atmospheric pressure
Answer: (B) Thermal expansion and contraction
38. Which of the following is an example of heat transfer mainly by convection?
(A) Heat from the Sun reaching Earth
(B) Heating of water in a pot
(C) Heat felt from a fire at a distance
(D) Heat passing through a metal rod
Answer: (B) Heating of water in a pot
39. Which of the following is correctly matched?
(A) Desert cooler — Condensation
(B) Pressure cooker — Lower boiling point
(C) Thermos flask — Minimization of heat transfer
(D) Woollen clothes — Good conduction
Answer: (C) Thermos flask — Minimization of heat transfer
40. Which of the following is incorrectly matched?
(A) Sea breeze — Convection
(B) Woollen clothes — Trapped air
(C) Pressure cooker — Higher boiling point
(D) Desert cooler — Condensation
Answer: (D) Desert cooler — Condensation
Explanation: A desert cooler works primarily through evaporation, not condensation.
Quick Revision: Heat & Thermal Physics
| Application | Principle |
|---|---|
| Sea breeze | Differential heating + convection |
| Land breeze | Differential heating + convection |
| Chimney | Convection |
| Ceiling ventilator | Hot air rises |
| Woollen clothes | Trapped air / poor conduction |
| Thermos flask | Reduces conduction, convection & radiation |
| Black surfaces | Good absorbers/emitters |
| White clothes | Reflect more radiation |
| Pressure cooker | Higher pressure → higher boiling point |
| Refrigerator | Removes heat from cold region |
| Desert cooler | Evaporation |
| Sweating | Evaporation |
| Earthen pot | Evaporation |
| Sawdust around ice | Poor conductor |
| Metal spoon | Good conductor |
| Railway track gaps | Thermal expansion |
| Slack electric wires | Thermal expansion/contraction |