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Valve Radio and Audio Repair Handbook by CHAS MILLER

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Chapter 1

Basic facts you need to know about electricity and magnetism

Electricity from batteries

There are two kinds of electricity, alternating current (AC), the kind that comes from the electricity mains, and direct current (DC), which is the kind that comes from batteries. Every battery has two poles or connections, one positive and one negative. Current drawn from a battery flows continuously in one direction only, hence the old alternative name of ‘continuous current’. Batteries may be subdivided into two classes known as primary and secondary types.

Primary batteries produce electricity from chemical action within ‘cells’ which continues until the chemicals become exhausted and the battery ‘runs down’. There are various combinations of chemicals ...

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