Physics Past Questions and Answers

The process by which a metal, heated to high temperature, gives off electrons from its surface is known as

An electric string of length l is elastically stretched through a length e by a force F. The area of cross- section of the string is A and its Young’s modulus is E. Which of the following expressions is correct?

(a) Explain what is meant by the following statement. The specific latent heat of fusion of ice is \(3.4 \times 10^{5}Jkg^{-1}\).
(b) Describe an experiment to determine the specific latent heat of fusion of ice. State two precautions necessary to obtain an accurate result.
(c) Using the kinetic theory of matter, explain why ice can change to water at 0°C without any change in temperature.

(a)(i) What is meant by resonance?
(ii) Outline the necessary steps taken in a simple experiment to illustrate top resonance
(iii) Explain why a vibrating tuning fork sounds louder when its stem is pressed against a table top than when held in air.
(b) Explain with the aid of diagrams, how a concave mirror could be used to: (i) Ignite a piece of carbon paper; (ii) produce an exact copy of a picture on a screen.

(a) Draw a simple labelled diagram illustrating the principle of a step-down transformer and explain how it works
(b) State three ways by which energy is lost in a transformer and how they can be minimized.
(c) If a transformer is used to light a lamp rated at 60W, 220V from a 4400V a.c. supply, calculate the; (i) ratio of the number of turns of the primary coil to the secondary coil in the transformer (ii) current taken from the main circuit if the efficiency of the transforme is 95%.