What is Heat? Heat is the form of energy that is transferred between two substances at different temperatures.Temperature is the degree of hotness or coldness of matter. Heating something implies facilitating the molecules to move faster. In simple terms, Heat is simply the transfer of energy from a hot object to a colder object. Heat Quiz lists some of the important questions for competitive exams from the topic Heat.
Heat vs. Temperature: Heat is a form of energy and Temperaturee is a measure of the amount of that energy present in a body.
Units of Heat: All forms of energy including heat can be converted into work. The two most commonly used units of heat are: Calorie and the British thermal unit (BTU). The calorie (or gram-calorie) is the amount of energy required to raise the temperature of one gram of water from 14.5° to 15.5° C; the BTU is the amount of energy required to raise the temperature of one pound of water from 63° to 64° F. Fact:One BTU is approximately 252 calories.

Heat Quiz - Important Questions
1. Woolen clothes are used in winter season because woollen clothes (a) are good sources for producing heat (b) absorb heat form surroundings (c) are bad conductors of heat (d) provide heat to body continuously Ans:c
2. Water has maximum density at (a) 0°C (b) 32°F (c) –4°C (d) 4°C Ans:d
3. Expansion during heating (a) occurs only in solids (b) increases the weight of a material (c) decreases the density of a material (d) occurs at the same rate for all liquids and solids Ans:c
4. When a copper ball is heated, the largest percentage increase will occur in its (a) diameter (b) area (c) volume (d) density Ans:c
5. If a liquid is heated in condition of weightlessness, the heat is transmitted through (a) conduction (b) convection (c) radiation (d) None, because the liquid cannot be heated in weightlessness Ans:a
6. Heat travels through vacuum by (a) conduction (b) convection (c) radiation (d) both (a) and (b) Ans:c
7. A bimetallic strip consists of brass and iron. When it is heated it bends into an arc with brass on the convex and iron on the concave side of the arc. This happens because (a) brass has a higher specific heat capacity than iron (b) density of brass is more than that of iron (c) it is easier to bend an iron strip than a brass strip of the same size (d) brass has a higher coefficient of linear expansion than iron Ans:d
8. The earth radiates in the infra-red region of the spectrum. The spectrum is correctly given by (a) Wien’s law (b) Rayleigh's law (c) Planck’s law of radiation (d) Stefan’s law of radiation Ans:c
9. Good absorbers of heat are (a) poor emitters (b) non-emitters (c) good emitters (d) highly polished Ans:c
10. Which of the following qualities suit for a cooking utensil (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 Ans:d
11. 5g ice at 0ºC is mixed with 5g of steam at 100ºC . What is the final temperature? (a) 50ºC (b) 100ºC (c) 80ºC (d) 150ºC Ans:b
12. By the first law of thermodynamics, for solids (a) dQ = dU + dW (b) dQ = dU (c) dQ = dW + dU (d) dQ = dU / dW Ans:c
13. There are four objects A, B, C and D. It is observed that A and B are in thermal equilibrium and C and D are also in thermal equilibrium. However, A and C are not in thermal equilibrium. We can conclude that – (a) B and D are in thermal equilibrium (b) B and D could be in thermal equilibrium but might not be A and D (c) B and D cannot be in thermal equilibrium (d) the zeroth law of thermodynamics does not apply here because there are more than three objects Ans:c
14. According to the kinetic theory of gases (a) all the atoms move horizontally with equal speeds (b) an atom moves faster during its downward motion than its upward motion (c) at any instant one-third of the total atoms are moving along x-axis (d) None of these Ans:c
15. The fastest mode of transfer of heat is (a) conduction (b) convection (c) radiation (d) None of these Ans:c
16. The wavelength of radiation emitted by a body depends upon (a) the nature of its surface (b) the area of its surface (c) the temperature of its surface (d) All of the above Ans:d
17. The sprinkling of water slightly reduces the temperature of a closed room because (a) temperature of water is less than that of the room (b) specific heat of water is high (c) water has large latent heat of vaporisation (d) water is a bad conductor of heat Ans:c
18. Which of the following is not close to a black body? (a) Black board paint (b) Green leaves (c) Black holes (d) Red roses Ans:a
19. A solid cube and a solid sphere of the same material have equal surface area. Both are at the same temperture 120°C , then (a) both the cube and the sphere cool down at the same rate (b) the cube cools down faster than the sphere (c) the sphere cools down faster than the cube (d) whichever is having more mass will cool down faster Ans:b
20. At a given temperature the internal energy of a substance (a) in liquid state is equal to that in gaseous state (b) in liquid state is less than that in gaseous state (c) in liquid state is more than that in gaseous state (d) is equal for the three states of matter Ans:b
21. Consider two identical iron spheres , one which lie on a thermally insulating plate, while the other hangs from an insulatory thread. Equal amount of heat is supplied to the two spheres Heat C-21 (a) Temperature of A will be greater than B (b) Temperature of B will be greater than A (c) Their temperature will be equal (d) Can’t be predicted Ans:b
22. Air conditioner is based on the principle of (a) Carnot cycle (b) refrigerator (c) first low of thermodynamics (d) None of these Ans:b
23. Gases exert pressure on the walls of the container because the gas molecules (a) possess momentum (b) collide with each other (c) have finite volume (d) obey gas laws Ans:a
24. Food in the pressure cooker is cooked faster, as (a) the boiling point increases due to an increase in pressure (b) the boiling point decreases due to an increase in pressure (c) more steam is available at 100°C (d) more pressure is available at 100°C Ans:a
25. A metal sheet with a circular hole is heated. The hole (a) gets larger (b) gets smaller (c) remains of the same size (d) gets deformed Ans:a
26. When water is heated from 0ºC to 10ºC, its volume (a) increases (b) decreases (c) does not change (d) first decreases and then increases Ans:b
27. A : At high altitude regions the cooking of food becomes difficult. B : Water boils at lower temperature when the pressure is low. (a) Both A and B are wrong. (b) A and B are correct and B is not the correct explanation of A. (c) A and B are correct and B is the correct explanation of A. (d) A is correct but B is wrong. Ans:c
28. When vapour condenses into liquid (a) it absorbs heat (b) it liberates heat (c) its temperature rises (d) its temperature decreases Ans:b
29. The temperature of the sun is measured with (a) Platinum thermometer (b) Gas theromometer (c) Pyrometer (d) Vapour pressure thermometer Ans:c
30. Two spheres of same size are made of the same metal but one is hollow and the other is solid. They are heated to same temperature, then (a) both spheres will expand equally (b) hollow sphere will expand more than the solid one (c) solid sphere will expand more than the hollow one (d) None of the above Ans:a
31. Heat is transmitted from higher to lower temperature through actual mass motion of the molecules in (a) conduction (b) convection (c) radiation (d) none of these Ans:b
32. The temperature of a room is 77°F. What would it be on the Celsius scale? (a) 25°C (b) 45°C (c) 60°C (d) 350°C Ans:a
33. Ventilators are provided at the top of room (a) to bring oxygen for breathing (b) so that sunlight may enter the room (c) to maintain conventional currents to keep the air fresh in the room (d) to provide an outlet for carbon dioxide Ans:c
34. What temperature is the same on celsius scale as well as on Fahrenheit scale? (a) – 212°C (b) – 40°C (c) – 32°C (d) 32°C Ans:b
35. Two holes of unequal diameters d1 and d2 (d1 > d2) are cut in a metal sheet. If the sheet is heated, (a) both d1 and d2 will decrease (b) both d1 and d2 will increase (c) d1 will increase, d2 will decrease (d) d1 will decrease, d2 will increase Ans:b
36. At 0°C a body emits (a) no radiation (b) only visible light (c) only microwave radiation (d) all wavelengths. Ans:d
37. Triple point is the temperature at which (a) matter may simultaneously exist in liquid and gaseous state. (b) matter may simultaneously exist in liquid and solid state. (c) matter may simultaneously exist in solid and gaseous state. (d) matter may simultaneously exist in all the three forms. Ans:d
38. In order that the heat flows from one part of a solid to another part, what is required? (a) Uniform density (b) Temperature gradient (c) Density gradient (d) Uniform temperature Ans:b
39. At a common temperature, a block of wood and a block of metal feel equally cold or hot. The temperatures of block and wood are (a) equal to the temperature of the body (b) less than the temperature of the body (c) greater than temperature of the body (d) either (b) or (c) Ans:a
40. The bulb of one thermometer is spherical, while that of other is cylindrical.If both of them have equal amount of mercury, which thermometer will respond quickly to the temperature? (a) spherical bulb (b) cylindrical bulb (c) elliptical bulb (d) both (a) and (c) Ans:b
41. Consider the following statements. (A) Some bodies may contract on heating (B) Water shows anamolous expansion. (a) (A) is true and (B) is false (b) (A) is false and (B) is true. (c) Both (A) and (B) are true. (d) Both (A) and (B) are false. Ans:c
42. The rate of flow of heat through a rod depends on: (a) thermal conductivity of the rod. (b) length of the rod. (c) temperature difference across the rod. (d) All of these Ans:d
43. Which of the following represents convection ? (a) Land breeze (b) Exhaust fan (c) Heating water by keeping the vessel on a flame (d) All of these Ans:d