Heat

What is the SI unit of heat?
a) Calorie
b) Joule
c) Watt
d) Kelvin
✅ b) Joule
Explanation: Joule is the SI unit of energy, including heat energy.

The process of heat transfer without movement of particles is:
a) Convection
b) Conduction
c) Radiation
d) Evaporation
✅ c) Radiation
Explanation: Radiation does not require a medium and occurs through electromagnetic waves.

The heat transfer in solids takes place mainly by:
a) Conduction
b) Convection
c) Radiation
d) Sublimation
✅ a) Conduction
Explanation: In solids, particles do not move; heat passes through vibration.

The mode of heat transfer in liquids and gases is:
a) Conduction
b) Convection
c) Radiation
d) Absorption
✅ b) Convection
Explanation: Heat is transferred by actual movement of fluid particles.

Which method of heat transfer can occur in a vacuum?
a) Conduction
b) Convection
c) Radiation
d) All three
✅ c) Radiation
Explanation: Only radiation does not require any medium.

Which thermometer is commonly used to measure human body temperature?
a) Barometer
b) Clinical thermometer
c) Laboratory thermometer
d) Digital voltmeter
✅ b) Clinical thermometer
Explanation: It ranges between 35°C to 42°C and uses mercury/alcohol.

Normal human body temperature is:
a) 98.4°F
b) 98.6°F
c) 99.6°F
d) 96.4°F
✅ b) 98.6°F
Explanation: Equivalent to 37°C in Celsius scale.

The device used to measure temperature is:
a) Thermometer
b) Barometer
c) Hygrometer
d) Calorimeter
✅ a) Thermometer
Explanation: Thermometers measure temperature using mercury or sensors.

Which of the following is a good conductor of heat?
a) Wood
b) Glass
c) Copper
d) Plastic
✅ c) Copper
Explanation: Metals are good conductors of heat and electricity.

Which material is a poor conductor (insulator) of heat?
a) Iron
b) Copper
c) Aluminium
d) Wool
✅ d) Wool
Explanation: Wool traps air and reduces heat transfer.

Which scale is NOT used to measure temperature?
a) Celsius
b) Kelvin
c) Fahrenheit
d) Joule
✅ d) Joule
Explanation: Joule is a unit of energy, not temperature.

Heat always flows from:
a) Cold to hot
b) Hot to cold
c) High pressure to low pressure
d) Low mass to high mass
✅ b) Hot to cold
Explanation: Heat flows in direction of temperature difference until equilibrium.

The boiling point of water in Celsius is:
a) 90°C
b) 100°C
c) 110°C
d) 212°C
✅ b) 100°C
Explanation: Standard atmospheric pressure boiling point is 100°C.

The freezing point of water is:
a) 0°C
b) 4°C
c) 32°C
d) 273°C
✅ a) 0°C
Explanation: Water freezes at 0°C = 32°F = 273K.

The Kelvin scale starts from:
a) -273 K
b) 0 K
c) 273 K
d) 100 K
✅ b) 0 K
Explanation: 0 Kelvin = absolute zero, the theoretical lowest temperature.

Which surface absorbs heat best?
a) White and rough
b) Shiny
c) Black and rough
d) Transparent
✅ c) Black and rough
Explanation: Dark surfaces absorb more radiation.

What is a calorimeter used for?
a) Measure temperature
b) Measure heat
c) Measure humidity
d) Measure sound
✅ b) Measure heat
Explanation: It measures amount of heat in physical/chemical processes.

Latent heat refers to:
a) Heat added that increases temperature
b) Heat added without temperature change
c) Heat measured in cold climates
d) Heat that reduces weight
✅ b) Heat added without temperature change
Explanation: It changes state (solid ↔ liquid ↔ gas), not temperature.

The amount of heat required to raise 1 gram of water by 1°C is:
a) 4.2 Joules
b) 1 Calorie
c) Both a and b
d) 100 Calories
✅ c) Both a and b
Explanation: 1 calorie ≈ 4.18 joules for water.

Which method of heat transfer is responsible for sea breeze?
a) Conduction
b) Radiation
c) Convection
d) Sublimation
✅ c) Convection
Explanation: Air moves due to differential heating of land and sea.

Expansion due to heat is called:
a) Thermal fusion
b) Thermal contraction
c) Thermal expansion
d) Latent expansion
✅ c) Thermal expansion
Explanation: Substances expand when heated.

The sun transfers heat to Earth by:
a) Conduction
b) Convection
c) Radiation
d) Diffusion
✅ c) Radiation
Explanation: Energy travels through space via electromagnetic waves.

Which of the following is not an effect of heat?
a) Expansion
b) Contraction
c) Change of state
d) Increase in pressure
✅ b) Contraction
Explanation: Most substances expand, not contract, when heated.

Which thermometer can measure very high temperatures?
a) Clinical
b) Digital
c) Pyrometer
d) Mercury
✅ c) Pyrometer
Explanation: Used to measure temperature of furnaces or kilns.

Thermal conductivity is highest in:
a) Silver
b) Wood
c) Air
d) Water
✅ a) Silver
Explanation: Among metals, silver conducts heat best.

Good absorbers of heat are also:
a) Good reflectors
b) Poor conductors
c) Good emitters
d) Transparent
✅ c) Good emitters
Explanation: Objects that absorb heat efficiently also radiate efficiently.

Unit of specific heat is:
a) J/kg
b) J/kg·K
c) N/m²
d) J/m³
✅ b) J/kg·K
Explanation: Specific heat = energy required to raise temp per kg per Kelvin.

Gases are heated mostly by:
a) Conduction
b) Radiation
c) Convection
d) Insulation
✅ c) Convection
Explanation: Hot gases rise and carry heat with them.

What is the primary cause of global warming?
a) Conduction
b) Convection
c) Excess heat retention due to greenhouse gases
d) Ocean currents
✅ c) Excess heat retention due to greenhouse gases
Explanation: Traps infrared radiation, increasing Earth's temperature.

Heat energy is measured by:
a) Barometer
b) Calorimeter
c) Thermometer
d) Multimeter
✅ b) Calorimeter
Explanation: Calorimeters measure amount of heat exchanged.

A metal feels colder than wood at the same temperature because:
a) It conducts heat better
b) It is shiny
c) It reflects more light
d) It insulates better
✅ a) It conducts heat better
Explanation: Metal draws heat away from skin faster.

Which is used to prevent heat loss in thermos flasks?
a) Vacuum
b) Water
c) Air
d) Foam
✅ a) Vacuum
Explanation: Vacuum layer prevents conduction and convection.

Which phase change requires latent heat absorption?
a) Freezing
b) Condensation
c) Melting
d) Cooling
✅ c) Melting
Explanation: Energy is absorbed without temperature rise.

What is the fixed point on Celsius scale for freezing?
a) 100°C
b) 0°C
c) -100°C
d) 273°C
✅ b) 0°C
Explanation: Reference temperature for freezing water.

How does heat travel in solids?
a) By radiation
b) By conduction
c) By convection
d) By vibration
✅ b) By conduction
Explanation: Solids do not flow, so heat is transferred via vibrations.

Which thermometer uses alcohol instead of mercury?
a) Laboratory
b) Clinical
c) Digital
d) Minimum-maximum
✅ d) Minimum-maximum
Explanation: Alcohol expands more and can be dyed for visibility.

Which of the following substances expands on cooling?
a) Iron
b) Water (0°C to 4°C)
c) Mercury
d) Copper
✅ b) Water (0°C to 4°C)
Explanation: Water shows anomalous expansion in this range.

Which gas traps the most heat in Earth’s atmosphere?
a) Nitrogen
b) Oxygen
c) Carbon dioxide
d) Helium
✅ c) Carbon dioxide
Explanation: CO₂ is a primary greenhouse gas.

What happens when heat is applied to a solid?
a) Only melts
b) Molecules vibrate more
c) Temperature decreases
d) Volume decreases
✅ b) Molecules vibrate more
Explanation: Vibration increases, leading to expansion or change of state.

Which is not a heat transfer method?
a) Conduction
b) Convection
c) Radiation
d) Compression
✅ d) Compression
Explanation: Compression affects pressure, not heat transfer.

Specific heat is defined as the heat required to:
a) Raise the temperature of 1 kg by 1 K
b) Raise any amount of substance
c) Boil a substance
d) Increase pressure
✅ a) Raise the temperature of 1 kg by 1 K
Explanation: It defines thermal capacity per unit mass.

Which of the following materials is used in fire-proof clothing?
a) Cotton
b) Wool
c) Asbestos
d) Nylon
✅ c) Asbestos
Explanation: It resists heat and is a poor conductor.

Heat energy is also known as:
a) Kinetic energy
b) Potential energy
c) Thermal energy
d) Electrical energy
✅ c) Thermal energy
Explanation: Internal energy due to particle motion.

Which metal is used in laboratory thermometers?
a) Aluminium
b) Copper
c) Mercury
d) Zinc
✅ c) Mercury
Explanation: Mercury expands uniformly with temperature.

Which color reflects the most heat?
a) Black
b) Red
c) White
d) Green
✅ c) White
Explanation: White surfaces reflect most incident radiation.

Heat is a form of:
a) Matter
b) Force
c) Energy
d) Pressure
✅ c) Energy
Explanation: Heat is energy transferred due to temperature difference.

The coldest possible temperature is:
a) 0°C
b) 273°C
c) 0 K
d) 100 K
✅ c) 0 K
Explanation: Known as absolute zero, particle motion ceases.

Which layer of Earth has highest temperature?
a) Crust
b) Mantle
c) Inner core
d) Outer core
✅ c) Inner core
Explanation: Due to immense pressure and radioactive decay.

Which method does NOT transfer heat in liquids?
a) Convection
b) Radiation
c) Conduction
d) Sublimation
✅ d) Sublimation
Explanation: Sublimation is a change of state, not a transfer method.

One calorie equals approximately:
a) 2 Joules
b) 4.2 Joules
c) 10 Joules
d) 100 Joules
✅ b) 4.2 Joules
Explanation: Standard conversion for energy units.