Physics Past Questions and Answers

Which of the following statements is not correct?

A A sea breeze is due to convection in air
B Cotton materials are better than woollen ones for use in hot weather
C Convectional currents play an important role in the cooling of the engine of a motor car
D The vacuum space in a flask helps to reduce heat loss by radiation.

Question 667:

Calculate the heat energy required to change 0.1kg of ice at 0^oC to water boiling at 100^oC. (Specific heat capacity of water = 4200 J kg^-1K^-1) (Specific latent heat of fusion of ice = 336,000 J kg^-1)

A 75,600J
B 336,000J
C 340,200J
D 378,000J.

Question 668:

Which of the following statements about evaporation is not correct?

A The rate of evaporation of a liquid varies with temperature
B The molecules of an evaporating liquid have an average speed
C Evaporation occurs when faster molecules escape from the surface of a liquid
D Evaporation takes place inside a liquid.

Question 669:

Calculate the power rating of an immersion heater used for 10 minutes to increase the temperature of 10kg of water by 15K. (Specific heat capacity of water = 4200 J l-1K^-1)

A 1,050W
B 16,800W
C 18,060W
D 20,160W

Question 670:

A ray of light is incident on 'a plane mirror at an angle of 20^o. This mirror is rotated through, twice this angle, In this new position the angle between the incident ray and the reflected ray is

A 20^o
B 40^o
C 80^o
D 120^o.