Heat and Temperature — 9 Physics PYQs with Answers | UKPSC PYQ Hub

Question 1

The thermal conductivity of a rod depends on :

Accepted Answer

Material of the rod. Thermal conductivity of a rod depends Upon the physical properties of the material of rod such as the nature of the material.

Question 2

The temperature of a healthy human beings body is– 370 370

Accepted Answer

C. The average normal body temperature is generally accepted as 98.6°F (37°C).

Question 3

The insulator of electricity is

Accepted Answer

Silk. The insulator of electricity is silk as it does not have any free electrons for the flow of the current.

Question 4

Pasteurization of milk is done at:

Accepted Answer

62.8º C for 30 minutes. In the process of Pasteurization of milk, it is heated to about 62.8º C for 30 minutes and then suddenly chilled and stored. By doing so, it prevents the growth of microbes. Pasteurized milk can be consumed without boiling as it is free from harmful microbes.

Question 5

With the rise of temperature, the viscosity of liquid:

Accepted Answer

Decreases. The viscosity of liquids decreases with temperature while it increases in the case of gases. Most of the fluids are not ideal ones and offer some resistance to motion. This resistance to fluid motion is like an internal friction analogous to friction when a solid moves on a surface. It is called viscosity. This force exists when there is relative motion between layers of the liquid.

Question 6

The heat required in calories to convert one- gram of ice at 0 ºC to steam at 100 ºC is approximately

Accepted Answer

716. Heat required to convert 1 g ice at 0ºC into steam at 100ºC is - First the ice at 0ºC should be converted to water at 0ºC , then to water at 100ºC and then to steam at 100ºC [Total heat required = ML + MC∆T + M L steam. ice = 1 [80+ 1 (100-0) + 536] = 716

Question 7

Food is cooked faster in a pressure cooker because

Accepted Answer

Due to high pressure the boiling point of water is raised.. Food is cooked faster in a pressure cooker because in a pressure cooker, increases the boiling point hence, generated which has greater thermal energy and this thermal energy is transferred to food to be cooked. Therefore, food is cooked faster.

Question 8

At what temperature is the density of water maximum?

Accepted Answer

4 °C. The density of water is maximum at 4°C.