Question 1

Which mode of heat transfer can occur through vacuum?

Accepted Answer

Radiation. Radiation transfers heat by electromagnetic waves, so it does not need a material medium. Conduction and convection need matter to pass energy. The Sun warms Earth mainly by radiation.

Question 2

Heat transfer due to bulk motion of a fluid is called?

Accepted Answer

Convection. Convection happens when heat is carried by moving fluid. Warm fluid becomes less dense and rises while cooler fluid sinks. Convection currents are common in water and air.

Question 3

Which material is generally the best conductor of heat?

Accepted Answer

Copper. Copper conducts heat very well because it has many free electrons. Insulators like wood and rubber resist heat flow strongly. Metals are generally good thermal conductors.

Question 4

The SI unit of thermal conductivity is?

Accepted Answer

W m⁻¹ K⁻¹. Thermal conductivity is measured in W m⁻¹ K⁻¹ in SI units. It tells how easily heat flows through a material. A larger value means faster conduction for the same conditions.

Question 5

In conduction, heat flows from?

Accepted Answer

higher temperature to lower temperature. Conduction transfers heat from a region of higher temperature to lower temperature. It occurs due to particle collisions and electron motion in solids. Heat flow stops when temperatures become equal.

Heat Transfer — Set 1