Thermal | MCQs

Explanation

Expansion of metal on heating is a physical change because it does not alter the metal’s chemical composition.

When cooled, the metal returns to its original size, showing that the change is reversible.

Explanation

Thermal power generation consists of using steam power 

Thermal energy sources are fossil fuels like:

natural gas, coal, and oil

as well as solar heat

heat pump electric heat

and geothermal heat.

Explanation

The correct preposition to use with "good" when referring to a skill or activity is "at."

Explanation

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

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

Explanation

The energy extracted from the vaporised liquid as evaporation occurs will decrease the temperature of the liquid, resulting in a process known as evaporative cooling.

Explanation

Answer:

D

Fans help by replacing hot and humid air with cooler, dry air that allows for more evaporation. Cold air evaporates sweat and creates a wind-cooling effect that cools us without affecting room temperature.

Explanation

Explanation

The average translational kinetic energy of a molecule is given by:

(3/2)kT = (3/2) × (1.38 × 10^-23 J/K) × T

Since the temperature is the same for both O2 and N2 molecules, the average translational kinetic energy will be the same:

0.048 eV = (3/2)kT

The mass of the molecule does not affect the average translational kinetic energy.

Therefore, the translational kinetic energy of N2 molecules at the same temperature is also:

0.048 eV

Explanation

Initial efficiency (η) = 40% = 0.4

Sink temperature (Tc) = 300 K

Initial source temperature (Th) = 300 / (1 - 0.4) = 500 K

New efficiency (η_new) = 0.4 + 0.5(0.4) = 0.6

New source temperature (Th_new) = 300 / (1 - 0.6) = 750 K

Increase in temperature = Th_new - Th = 750 - 500 = 250 K

Explanation