Thermal | MCQs

Explanation

Tin has the lowest melting point (~232°C) among.

• Zinc (~419°C)
• Gold (~1064°C)
• Lead (~327°C)

Explanation

A computer works by electrical signals.

"By" is used to indicate the means or method by which the action is performed

Explanation

Linear thermal expansion of a solid depends on:

• Increase in temperature
• Original length
• Properties of the material

Explanation

Specific heat capacity is the thermal energy transfer required per unit mass to increase the temperature of a substance by 1°C (or 1 K).

It is a measure of how much heat energy a substance can absorb or release per unit mass per unit temperature change.

Explanation

Heat capacity is the amount of heat energy required to change the temperature of a substance by a given amount.

It is calculated as the product of the mass of the substance and its specific heat capacity:

Heat Capacity = mass x specific heat capacity

Explanation

Efficiency is the ratio of output to input, often expressed as a percentage.

It represents how much of the input energy is actually converted into useful output energy, with the rest being lost as waste or heat.

Key Points:

• Energy is the ability to do work.
• Work is the transfer of energy through a force applied over a distance.
• Power is the rate at which work is done or energy is transferred.

Explanation

When a gas changes into a liquid, the molecules:

• Move closer together (their distance decreases)
• Lose kinetic energy (they slow down)

Explanation

When a gas is heated in a container of fixed volume, the molecules of the gas:

• Move faster (their kinetic energy increases, causing them to move more rapidly)
• Collide more frequently with the container walls (resulting in increased pressure)
• Do not expand (the container volume is fixed)
• Do not move further apart (the density of the gas remains the same, as the volume

Explanation

When a gas is heated in a sealed cylinder:

• The temperature of the gas increases (by definition of heating).
• The average kinetic energy of the particles increases (as the temperature rises, the molecules move faster).
• The pressure inside the container increases (as the molecules move faster and collide more frequently with the container walls).

Explanation

• Air expands the most for a given rise in temperature, due to its low density and high thermal expansion coefficient.
• This is why hot air rises and cool air sinks, driving convection currents in the atmosphere.