Heat

Total Questions: 49

31. Energy travels from Sun to Earth through-. [S.S.C. Online Graduation Level (T-I) 31.08.2016 (Shift-I)]

(a) conduction
(b) convection
(c) radiation
(d) modulation

Correct Answer: (c) radiation

Solution:Radiation — Heat transfer through electromagnetic waves without involving molecules or any medium. It can occur even in a vacuum.

Example: Heat from the Sun reaching Earth.

32. Which of the following is a process in which hot, less dense materials rise upward and are replaced by colder, more dense materials? [S.S.C. Online CGL (T-I) 13.08.2021 (Shift-I)]

(a) Convection
(b) Condensation
(c) Radiation
(d) Conduction

Correct Answer: (a) Convection

Solution:Convection is the transfer of heat by the movement of fluids (liquids or gases). In this process:

Hot, less dense fluid rises.
Cooler, denser fluid sinks.
This creates a circulating flow known as a convection current.

33. At room temperature, the metal that remains liquid is: [S.S.C. Online Graduation Level (T-I) 10.09.2016 (Shift-I)]

(a) Platinum
(b) Lead
(c) Mercury
(d) Zinc

Correct Answer: (c) Mercury

Solution:Mercury is the d-block element in the periodic table.

In the chemical world, only this metal remains in liquid form at ordinary temperature and pressure.
Mercury is rarely found in the free state, but its main ore is cinnabar (HgS).
When cinnabar is oxidized in the air, mercury is liberated.

34. Two bodies are in thermal equilibrium, if they are the same_________. [S.S.C. Online MTS (T-I) 9.10.2017 (Shift-III)]

(a) Temperature
(b) Amount of heat
(c) Mass
(d) Velocity

Correct Answer: (a) Temperature

Solution:Two bodies are in thermal equilibrium, if they are the same temperature.

When two objects are in thermal contact, heat flows from the hotter object to the cooler one.
Eventually, when no net heat flows between them, they are said to be in thermal equilibrium.
This occurs only when their temperatures are equal.

35. With the increase in temperature, the density of substance, in general _________ . [S.S.C. Online MTS (T-I) 19.09.2017 (Shift-III)]

(a) increases
(b) decreases
(c) will remain the same
(d) first decreases and then increases

Correct Answer: (b) decreases

Solution:Generally, due to an increase in the kinetic energy of the molecules of a substance, they move away from each other.

Therefore, in this case, the density of the substance decreases as the volume increases.

36. The English physicist James Prescott Joule out lined the basis of the_________. [S.S.C. Online MTS (T-I) 14.10.2021 (Shift-II)]

(a) phenomenon of gravitation
(b) theory of vibrating receptacle
(c) principle of energy conservation
(d) concept of diffusion of gases

Correct Answer: (c) principle of energy conservation

Solution:James Prescott Joule studied the nature of heat and found its relationship with mechanical work.

It was on this basis that he laid the foundation of the energy conservation theory.
first law of thermodynamics.
This principle states that energy can neither be created nor destroyed, only transformed from one form to another.

37. Under what conditions do real gases behave like ideal gases? [C.P.O. S.I. 5.06.2016 (Shift-II)]

(a) high pressure and low temperature
(b) low pressure and high temperature
(c) high pressure and high temperature
(d) low pressure and low temperature

Correct Answer: (b) low pressure and high temperature

Solution:A real gas can act as an ideal gas at low pressure and high temperature.

38. Name the law in Physics that states an equal volume of all gases under the same conditions of temperature and pressure contains equal number of molecules. [S.S.C. Online Graduation Level (T-I) 5.03.2020 (Shift-I)]

(a) Ohm's Law
(b) Avogadro's Law
(c) Boyles's Law
(d) Charles's Law

Correct Answer: (b) Avogadro's Law

Solution:Avogadro's law is a gas law which states that the total number of atoms/molecules of a gas (i.e., the amount of gaseous substance) is directly proportional to the volume occupied by the gas at constant temperature and pressure.

That is, V1/n1 = V2/n2
here
V1 and V2 are the volumes of the gases,
and n1 and n2 are the number of moles of them).

39. Which law states that the volume of an ideal gas at constant pressure is directly proportional to the absolute temperature? [S.S.C. Online CHSL (T-I) 13.10.2020 (Shift-I)]

(a) Joule's Law
(b) Charles's Law
(c) Avogadro's Law
(d) Boyle's Law

Correct Answer: (b) Charles's Law

Solution:Charles's law states that the volume occupied by a fixed amount of gas is directly proportional to its absolute temperature if the pressure remains constant.
That means
V1/T1 = V2/T2
Here,
V1 and V2 are volumes of the gas,
and T1 and T2 are absolute temperatures.

40. At the boiling point of liquids, it's- [S.S.C. Online Graduation Level (T-I) 27.08.2016 (Shift-III)]

(a) Temperature increases
(b) Atmospheric pressure increases
(c) Temperature remains constant
(d) Vapour pressure decreases

Correct Answer: (c) Temperature remains constant

Solution:The temperature remains constant at the boiling point of the liquid, because the energy that is used to boil the liquid is spent breaking the intermolecular bonds between them, while the kinetic energy of the molecules remains the same.

Hence the temperature remains the same till all the molecular bonds are broken i.e. liquid does not vaporize.

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