. Electronic apparatus for biological research. Electronic apparatus and appliances; Biology -- Research. INTRODUCTION Pieces of electronic apparatus are complexes of'active' and 'passive' elements. Active elements are to be regarded as sources of electrical energy, whilst the passive elements either consume energy or modify it in some way. For an electrical circuit to be possible at least one element of each kind must be present. In developing a systematic theory of such circuits a problem of the chicken-and-the-egg variety arises—how to study one set of elements without having first discusse
. Electronic apparatus for biological research. Electronic apparatus and appliances; Biology -- Research. INTRODUCTION Pieces of electronic apparatus are complexes of'active' and 'passive' elements. Active elements are to be regarded as sources of electrical energy, whilst the passive elements either consume energy or modify it in some way. For an electrical circuit to be possible at least one element of each kind must be present. In developing a systematic theory of such circuits a problem of the chicken-and-the-egg variety arises—how to study one set of elements without having first discussed the other. The important active elements, in practical form, are of two kinds: (1) those which actually produce electrical energy—batteries, the supply mains and certain transducers; (2) those which only control the flow of energy derived from elsewhere, but which are treated as if they were themselves the source of it—valves, transistors, and the remainder of the transducers. The passive elements are resistance, capacitance, and inductance, pro- perties reahzed either in a specific component, a resistor, which is a device for exhibiting the property of resistance, or otherwise, as in the resis- tance of an electrophysiological preparation as measured between two elec- trodes. It may be remarked in passing that such a preparation is to be regarded as an active element of the first kind at the site of recording, but as passive at a site of stimulation. Since it is not possible to get very far discussing the active devices without introducing some passive ones it is usual to begin by considering the latter, and this we shall do, beginning in the next chapter. To investigate the properties of the passive elements, however, both singly and in combination, we need some ideal, generalized kinds of active element which we shall simply call 'generators'. A 'load' is to be understood as any passive element or arrangement of such elements into which these generators may work
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