The electric force between two point charges each of the magnitude, q at a distance of r apart in air of permittivity is:

(a) What is meant by the statement: The linear expansivity of a solid is \(1.0 \times 10^{-5}K^{-1}\)?

(b)(i) Describe an experiment to determine the linear expansivity of a steel rod. (ii) Steel bars, each of length 3m at 29°C are to be used for constructing a rail line. If the linear expansivity of steel is \(1.0 \times 10^{-5}K^{-1}\), calculate the safety gap that must be left between successive bars if the highest temperature expected is 41°C.

(c) State three advantages and two disadvantages of thermal expansion of solids. 

(a) What is a wave motion?

The equation \(y = A \sin \frac{2\pi}{\lambda} (Vt-X)\) represents a wavetrain in which y is the vertical displacement of a particle at distance X from the origin in the medium through which the wave is travelling. Explain, with the aid of a diagram, what A and \(\lambda\) represent.

(b) (i) Describe an experiment to determine the frequency of a note emitted by a source of sound

(ii) A pipe closed at one end is 1 m long. The air in the pipe is set into vibration and a fundamental note is produced. If the velocity of sound in air is 340ms\(^{-1}\), calculate the frequency of the note

(c) State two differences between a sound wave and a radio wave. 

(a) State the laws of electromagnetic induction.

(b) (i) Describe a simple experiment to show how an induced e.m.f, can be produced; (ii) State two factors on which the magnitude of the induced e.m.f. depends

(c) Explain what is meant by the r.m.s. value of an alternating current

(d) (i) If the alternating current is represented by \(I = l_{o} \sin \omega t\), state what the symbol \(I, I_{o}, \omega\) and \(\omega t\)represent.

(ii) Calculate the instantaneous value of such a current, if in a circuit it has r.m.s value of 15.0A when its phase angle is 30°.