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Heat Class 7 MCQ. We covered all the Heat Class 7 MCQ in this post for free so that you can practice well for the exam.
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MCQ on Heat for Class 7th Students
A metal piece is heated from 27 °C to 52 °C. By approximately what factor does its rate of radiation increase? ( Heat Class 7 MCQ )
(A) 1.36 times
(B) 2 times
(C) 2.72 times
(D) 4.08 times
Option a – 1.36 times
During conduction, the heat transferred per unit time across a unit area of a metallic plate is influenced by ( Heat Class 7 MCQ )
(A) the metal’s density
(B) the temperature gradient perpendicular to the surface
(C) the temperature to which the metal is heated
(D) the plate’s area
Option b – the temperature gradient perpendicular to the surface
A body cools at 0.6 °C/s when it is 40 °C warmer than its surroundings. What is the cooling rate when it is 20 °C above the surroundings?
(A) 0.2 °C/s
(B) 0.3 °C/s
(C) 0.6 °C/s
(D) 0.4 °C/s
Option b – 0.3 °C/s
A copper rod with length 10 cm and cross-sectional area 100 cm² needs to conduct heat at 4000 J/s. If the thermal conductivity of copper is 400 W/m·°C, what temperature difference is required between the ends? ( Heat Class 7 MCQ )
(A) 1 °C
(B) 10 °C
(C) 100 °C
(D) 1000 °C
Option c – 100 °C
A body’s temperature drops from 50 °C to 49.9 °C in 20 seconds. Assuming Newton’s law of cooling and surrounding temperature of 30 °C, how much time will it take to cool from 40 °C to 39.9 °C?
(A) 10 s
(B) 40 s
(C) 2.5 s
(D) 5 s
Option b – 40 s
Two rods of the same material and cross-sectional area are 0.6 m and 0.8 m in length. The temperature ends for the first rod are 100 °C and 70 °C, and for the second, 160 °C and 120 °C. Which one conducts heat at a higher rate? ( Heat Class 7 MCQ )
(A) First
(B) Second
(C) Both conduct equally
(D) Either one could conduct more
Option c – Both conduct equally
A surface has an absorption coefficient of 0.4 and a reflection coefficient of 0.6. Which statement best describes this surface? ( Heat Class 7 MCQ )
(A) It has emissive power of 0.2
(B) It has transmission power of 0.2
(C) It is completely transparent
(D) It is completely opaque
Option d – It is completely opaque
Identical rods made of copper and iron are coated with wax. When one end is placed in boiling water, the wax melts up to 8.8 cm in copper and 4.4 cm in iron. If copper’s thermal conductivity is 0.92, what is iron’s thermal conductivity?
(A) 0.23
(B) 0.46
(C) 0.115
(D) 0.69
Option a – 0.23
A calorie is the heat required to raise the temperature of 1 g of water by 1 °C under which condition? ( Heat Class 7 MCQ )
(A) From 14.5 °C to 15.5 °C at 760 mm Hg
(B) From 98.5 °C to 99.5 °C at 760 mm Hg
(C) From 13.5 °C to 14.5 °C at 76 mm Hg
(D) From 3.5 °C to 4.5 °C at 76 mm Hg
Option a – From 14.5 °C to 15.5 °C at 760 mm Hg
A surface absorbs 25% of incident heat and reflects 40 calories out of 100. What is the transmission coefficient?
(A) 0.25
(B) 0.35
(C) 0.4
(D) 0.5
Option b – 0.35
For a certain gas, if the ratio of specific heats is 3:2, what is the value of Cp? ( Heat Class 7 MCQ )
(A) R
(B) 2R
(C) 3R
(D) 5R
Option c – 3R
Air is not a good conductor, yet thermos flasks are evacuated between walls. Why?
(A) Filling air inside is impractical
(B) Air pressure may damage the flask
(C) Heat transfer by convection is possible in air
(D) Air provides no thermal advantage
Option c – Heat transfer by convection is possible in air
Identify the incorrect statement related to global warming and the greenhouse effect. ( Heat Class 7 MCQ )
(A) Polar ice is melting rapidly
(B) Coastal areas risk submersion
(C) Day length exceeds 24 hours
(D) Day length becomes shorter than 24 hours
Option d – Day length becomes shorter than 24 hours
A body receives ‘p’ joules of heat, out of which ‘q’ joules are reflected and transmitted. What is its absorption coefficient? ( Heat Class 7 MCQ )
(A) p/q
(B) q/p
(C) (q – p)/p
(D) (p – q)/p
Option d – (p – q)/p
Three litres of water at 27 °C are heated with a 1 kW coil. Heat is lost at 160 J/s from the open lid. How long will it take to reach 77 °C? (Specific heat of water = 4.2 kJ/kg)
(A) 7 min
(B) 6 min 2 s
(C) 12 min 30 s
(D) 14 min
Option c – 12 min 30 s
Two liquids at 60 °C and 20 °C are mixed. Their mass ratio is 4:5, and specific heat ratio is 4:3. What is the final temperature? ( Heat Class 7 MCQ )
(A) 70 °C
(B) 50 °C
(C) 40 °C
(D) 35 °C
Option d – 35 °C
A metal rod of length 1 m and area 100 cm² has one end at 100 °C and the other at 0 °C. With thermal conductivity of 100 W/m·K, how much heat flows through it per minute?
(A) 3 × 10³ J
(B) 6 × 10³ J
(C) 9 × 10³ J
(D) 12 × 10³ J
Option b – 6 × 10³ J
Half of an ice block is covered in black cloth, the other half in white. After sun exposure, which part melts more? ( Heat Class 7 MCQ )
(A) White-covered section
(B) Black-covered section
(C) Both melt equally
(D) Depends on ambient temperature
Option b – Black-covered section
If the temperature of a perfect black body is halved, how is its peak emission wavelength affected? ( Heat Class 7 MCQ )
(A) Increases fourfold
(B) Becomes half
(C) Doubles
(D) Becomes one-fourth
Option c – Doubles
A metal rod has its ends maintained at 100 °C and 120 °C, resulting in a heat transfer rate of 4.0 J/s. If the end temperatures are changed to 200 °C and 220 °C, what will be the new rate of heat transfer?
(A) 2 J/s
(B) 16 J/s
(C) 8.0 J/s
(D) 4.0 J/s
Option d – 4.0 J/s
A 500 g sample of lead releases 1600 calories of energy when cooled from 90 °C to 10 °C. Determine its specific heat capacity. ( Heat Class 7 MCQ )
(A) 0.004 cal/g °C
(B) 4.4 cal/g °C
(C) 0.04 cal/g °C
(D) 0.4 cal/g °C
Option c – 0.04 cal/g °C
When a piece of iron is heated in a flame, it changes from dull red to reddish yellow and finally to white hot. Which law best explains this behavior? ( Heat Class 7 MCQ )
(A) Stefan’s law
(B) Wien’s displacement law
(C) Kirchhoff’s law
(D) Newton’s law of cooling
Option b – Wien’s displacement law
A black body radiates energy at temperatures T₁ and T₂ where T₂ > T₁. The frequency at which the maximum energy is emitted is
(A) greater at T₁
(B) greater at T₂
(C) same for both T₁ and T₂
(D) unrelated to temperature
Option b – greater at T₂
Two kilograms of water at 60 °C is mixed with one kilogram of water at 30 °C in a container with a heat capacity of 200 J/K. If the specific heat of water is 4200 J/kg K, what is the approximate final temperature? ( Heat Class 7 MCQ )
(A) 55 °C
(B) 50 °C
(C) 45 °C
(D) 35 °C
Option b – 50 °C
Assertion: A black body radiates 16 times more energy per unit area per second if its temperature is doubled.
Reason: This occurs due to Stefan’s law.
(A) Both assertion and reason are true; reason correctly explains the assertion
(B) Both assertion and reason are true; reason does not explain the assertion
(C) Assertion is true, reason is false
(D) Assertion is false, reason is true
Option a – Both assertion and reason are true; reason correctly explains the assertion
Assertion: For a solid with thermal conductivity 4, its thermal resistivity equals 0.25.
Reason: Thermal resistivity is the inverse of thermal conductivity.
(A) Both assertion and reason are true; reason correctly explains the assertion
(B) Both assertion and reason are true; reason does not explain the assertion
(C) Assertion is true, reason is false
(D) Assertion is false, reason is true
Option a – Both assertion and reason are true; reason correctly explains the assertion
200 g of water at 50 °C is added to 100 g of ice at 0 °C. What is the final temperature of the system once equilibrium is reached? ( Heat Class 7 MCQ )
(A) 3.33 °C
(B) 6.66 °C
(C) 9.99 °C
(D) 16.66 °C
Option b – 6.66 °C
Three objects of equal material but different masses m, 2m, and 3m have temperatures of 40 °C, 50 °C, and 60 °C respectively. What will be the final equilibrium temperature when they are brought into contact?
(A) 58 °C
(B) 53 °C
(C) 35 °C
(D) 48 °C
Option b – 53 °C
When 2.5 kg of ice melts at 0 °C and its volume reduces by 10%, and given latent heat is 80 kcal/kg, what can be inferred about the internal latent heat?
(A) 80 kcal/kg
(B) Greater than 80 kcal/kg
(C) Less than 80 kcal/kg
(D) Zero
Option b – Greater than 80 kcal/kg
A body cools at 3 °C/min when it is at 50 °C. If the ambient temperature is 25 °C, what is the cooling rate when the body is at 40 °C? ( Heat Class 7 MCQ )
(A) 2 °C/min
(B) 1.5 °C/min
(C) 1.2 °C/min
(D) 1.8 °C/min
Option d – 1.8 °C/min
Two rods made of different materials have ends with identical temperature differences. Their thermal conductivities, radii, and lengths are in a 1:2 ratio. If the heat transfer rate through the larger rod is 8 cal/s, what is the heat flow through the smaller rod?
(A) 2
(B) 1
(C) 8
(D) 16
Option a – 2
A body cools from 100 °C to 70 °C in 8 minutes. If the ambient temperature is 15 °C, how long will it take to cool from 70 °C to 40 °C?
(A) 14 minutes
(B) 7 minutes
(C) 8 minutes
(D) 16 minutes
Option a – 14 minutes
When 1 gram of ice is mixed with 1 gram of steam, the resulting temperature at equilibrium is ( Heat Class 7 MCQ )
(A) 50 °C
(B) 0 °C
(C) 55 °C
(D) 100 °C
Option d – 100 °C
A black body is initially at 327 °C and reaches 927 °C. If its initial energy is 2 kJ, how much energy does it possess at the higher temperature?
(A) 32 kJ
(B) 320 kJ
(C) 1200 kJ
(D) 120 kJ
Option a – 32 kJ
Which type of utensil is most efficient for cooking food? ( Heat Class 7 MCQ )
(A) High specific heat and low thermal conductivity
(B) High specific heat and high thermal conductivity
(C) Low specific heat and low thermal conductivity
(D) Low specific heat and high thermal conductivity
Option d – Low specific heat and high thermal conductivity
Heat flows within a solid from one part to another when which of the following is present?
(A) Constant density
(B) Density gradient
(C) Temperature gradient
(D) Constant temperature
Option c – Temperature gradient
Mud houses stay cool in summer and warm in winter mainly because ( Heat Class 7 MCQ )
(A) Mud is a superconductor of heat
(B) Mud is a good conductor of heat
(C) Mud is a poor conductor of heat
(D) Mud reflects thermal radiation
Option c – Mud is a poor conductor of heat
A metal rod is 50 cm long with a cross-sectional area of 5 cm². Its ends are maintained at 25 °C and 125 °C. If the thermal conductivity is 0.092 kcal/ms°C, the temperature gradient is
(A) 2 °C/cm
(B) 2 °C/m
(C) 20 °C/cm
(D) 20 °C/m
Option a – 2 °C/cm
A metallic sphere drops in temperature from 64 °C to 55 °C in 10 minutes, and then from 55 °C to 42 °C in the next 10 minutes. What is the ratio of temperature fall rates during the two intervals?
(A) 9/10
(B) 13/10
(C) 9/13
(D) 13/9
Option c – 9/13
Which of the following cylindrical rods will allow the greatest heat conduction when both ends are kept at the same temperature? ( Heat Class 7 MCQ )
(A) Length 1 m, radius 1 cm
(B) Length 2 m, radius 1 cm
(C) Length 2 m, radius 2 cm
(D) Length 2 m, radius 4 cm
Option d – Length 2 m, radius 4 cm
We covered all the heat class 7 MCQ above in this post for free so that you can practice well for the exam.
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