Tag: physics

Questions Related to physics

Sugar particles slowly dissolve in water. This shows

particles of a gas ideal gases physics

  1. Refractive properties of water

  2. Motion of molecules in a substance

  3. Motion of substance

  4. Magic

Show answer
Correct Option: B
Explanation:

Sugar mixes in water because of motion of sugar molecules around water molecules.Overall a diffusion process is seen in it as sugar particles diffuse into water particles.

Speed of molecules is _______ in hot water than in cold water

particles of a gas ideal gases physics

  1. more

  2. less

  3. equal

  4. less than or equal to

Show answer
Correct Option: A
Explanation:

As molecules are heated, they gain kinetic energy and hence speed.We already know that kinetic energy is proportional to temperature of random moving particles.

Smoke rising from chimneys is example of

particles of a gas ideal gases physics

  1. Thermionic radiation

  2. Heating of molecules in a substance

  3. Motion of molecules in a substance

  4. Heat radiation

Show answer
Correct Option: C
Explanation:

Due to diffusion, smoke molecules leave the chimney and spreads in the atmosphere.Overall a diffusion process is seen in it as smoke particles diffuse into air particles.

Heating a liquid expands it because

particles of a gas ideal gases physics

  1. Molecules gain potential energy and due to it, motion of molecules is increased

  2. Molecules gain kinetic energy and due to it, motion of molecules is increased

  3. Molecules gain kinetic energy and due to it, motion of molecules is reduced

  4. Molecules gain potential energy and due to it, motion of molecules is reduced

Show answer
Correct Option: B
Explanation:

As a liquid is heated, its molecules gain kinetic energy, motion of molecules is increased and the liquid expands.Overall interparticle distance increases.

In convection,

particles of a gas ideal gases physics

  1. Heat transfers by radiation of infrared waves

  2. Heat transfers by motion of molecules in a substance

  3. Heat transfers by collision of molecules

  4. All of the above

Show answer
Correct Option: B
Explanation:

In convection, heat transfer occurs because of motion of molecules of substance in upward direction.Convection, occurs due to temperature differences which affect the density, and thus relative buoyancy, of the fluid. Heavier (more dense) components will fall, while lighter (less dense) components rise, leading to bulk fluid movement.

Water is a universal solvent. During mixing,

particles of a gas ideal gases physics

  1. Molecules of the water are distributed uniformly across the solute.

  2. Molecules of the solute are distributed uniformly across the volume of water.

  3. Molecules of the solute and molecules of water both move very fast to make the solution.

  4. None of the above

Show answer
Correct Option: B
Explanation:

As a solute is added to the water and mixed, its molecules are spread across the volume of water and solute is then dissolved in water.

Due to motion of molecules in a substance

particles of a gas ideal gases physics

  1. Smell of perfume spreads around the room

  2. Perfume bottle spreads around the room

  3. Perfume cools the room

  4. None of the above

Show answer
Correct Option: A
Explanation:

When perfume is sprayed in corner of a room, its molecules moves around the room due to diffusion spreading the fragrance. Overall a diffusion process is seen in it as perfume particles diffuse into air particles.

The temperature of the black body that radiates heat at a rate of $459.27 \times 10^4 W m^{-2}$ is:

laws of heat transfer heat and thermodynamics physics

  1. 1000K

  2. 2000K

  3. 3000K

  4. 4000K

Show answer
Correct Option: B

Which one of the following is the characteristic of Planck's quantum theory of radiation?

laws of heat transfer heat and thermodynamics physics

  1. The energy is not absorbed or emitted in integral multiple of quantum of energy.

  2. Radiation energy is not emitted or absorbed continuously but in the form of small packets of energy

  3. Radiation energy is emitted or absorbed continuously

  4. The magnitude of energy associated with a quantum is inversely proportional to its frequency

Show answer
Correct Option: B
Explanation:

According to Planck's quantum theory, radiation is emitted in the form of small packets of energy and is not continuous. Quantum of energy can be expressed by the relation E=hv, where h is Planck's constant and v is the frequency.

Pervost's theory of heat exchange is not applicable at temperature

laws of heat transfer heat and thermodynamics physics

  1. $0^oR$

  2. $0^oC$

  3. $0 K$

  4. $0^oF$

Show answer
Correct Option: C
Explanation:

Prevost postulated that  radiative equilibrium is the condition where a steady state system is in dynamic equilibrium, with equal incoming and outgoing radiative flux and negligible heat transfer by conduction and convection.
So by extended logic, at $0K$ equilibrium cannot be reached.