Table of contents

The author describes an analogue computer designed to demonstrate the equations of motion of simple systems, particularly simple harmonic ones. The design, performance and approximate costs are discussed.

The author discusses the general concept of the feedback classroom. A simple system using a unit employing mechanical switching is described. Various methods of using this facility are discussed.

An exciton is a quantum of electronic excitation energy travelling in the periodic structure of a crystal; it is electrically neutral and hence its movement through the crystal gives rise to the transportation of energy but not charge. This is a concise description of the ideal exciton. The authors give a more physical picture, show some of the interesting properties, their observation and the importance of the concept of excitons in relation to metals and insulators.

Discusses the power of the objective in terms of lateral and linear magnification, in comparison with microscope objective power.

The author discusses the representation and symbolization of the plane angle in certain equations of mathematics and physical science.

The strong dependence of the forces between magnets on their separation or orientation can be used to demonstrate some of the properties of oscillating systems. Ring magnets are very suitable for this type of demonstration because it is rather easy to arrange the mechanical constraint necessary to give a stable equilibrium position about which the oscillations take place.