Electronics Calculations Data Handbook

3

Direct current

AC and DC signals

We often hear electrical signals classified as ‘AC’ or ‘DC’. These abbreviations stand for the terms ‘alternating current’ and ‘direct current’, but they are applied as much to voltages as to currents. In this chapter we will talk about DC. Given that we understand Ohm’s Law, stated in Chapter 2, we have actually covered most of what ground there is. We will also introduce the term ‘power’ and consider its implications, which are important.

Direct current

A DC current is one which flows in one direction only. If we were to connect a resistor between the two terminals of a battery a DC current would result. For conventional current, it would flow from the positive terminal to the negative and have a magnitude, ...