Physics Past Questions and Answers

The design of the thermostat of an electric iron is based on the

A Emmision of electrons from metals when heated
B Increase in size of metals when heated
C Increase in the density of metals when heated
D Change in the mass of metals when heated

Question 1227:

A metal rod of length 50cm is heated from 40^oC to 80^oC. If the linear expansivity of the material is \(\alpha\), calculate the increase in length of the rod (in metres) in terms of \(\alpha\)

A 20\(\alpha\)
B 200\(\alpha\)
C 2000\(\alpha\)
D 20000\(\alpha\)

Question 1228:

The cubic expansivity of a certain gas at constant pressure is \(\frac{1}{273} k^{-1}\). If a given mass of the gas is held at constant pressure and its volume at 0^oC is 273m³, determine the volume of the gas at 273^oC.

A 273m³
B 546m³
C 819³
D 1092³

Question 1229:

Water of mass 1.5kg is heated from from 30^oC to 80^oC using an electric kettle which is rated 5A, 230V. Calculate the time taken to reach the final destination [specific heat capacity of water 4200Jkg^-1K^-1]

A 4.57 minutes
B 5.02 minutes
C 7.30 minutes
D 10.04 minutes

Question 1230:

The working principle of a pressure cooker is based on the

A Increase in the volume of steam inside it
B Complete trapping of heat inside it
C Increase in the pressure of the pot
D Decrease in the pressure of the pot