WAEC Physics 1994 Past Questions

(a) What is meant by the statement: The specific heat capacity of copper is \(400 J kg^{-1}K^{-1}\)?

(b)(i) Describe an experiment to determine the specific heat capacity of copper using a copper ball.

(ii) State two precautions necessary to obtain accurate results

(iii) A piece of copper ball of mass 20 g at 200°C is placed in a copper calorimeter of mass 60 g containing 50 g of water at 30°C, ignoring heat losses, calculate the final steady temperature of the mixture (Specific heat capacity of water = \(4.2 J g^{-1}K^{-1}\)) (Specific heat capacity of copper = \(0.4 Jg^{-1}K^{-1}\)).

(a) Describe an experiment to show how the frequency of the note emitted by a vibrating string depends on the tension in the string

(b) Draw diagrams showing a vibrating string fixed at both ends emitting (i) fundamental frequency (ii) second overtone indicate the nodes and antinodes on the diagrams

(c) With the aid of a ray diagram show how a virtual image of an object is formed by a (i) concave mirror (ii) converging lens 

(a) Explain what is meant by a magnetic field

(b)(i) Describe an experiment to show that a magnetic field exists around a straight wire carrying current

(ii) Draw a labelled diagram showing the pattern and direction of the magnetic field rroduced around the wire. (Neglect the earth's magnetic field).

(c) Sketch the magnetic field due to two straight parallel wires carrying current in the same direction. Indicate the neutral point in the field

(d) Explain, with the aid of a labelled diagram, how a delicate magnetic material could be protected from the earth's magnetic field.

(a) State the laws of electromagnetic induction

(b) Explain how one of the laws illustrates the principle of conservation of energy

(c)(i) Draw a labelled diagram of a simple d.c. electric motor and explain how it works.

(ii) State two reasons why the efficiency of an electric motor is less than 100%.