Waveform and Frequency

Current can be generated as either pulsed direct current (DC) (Figure 2a), as from a battery switched on and off, which flows in one direction; or it can be an alternating current (AC) (Figure 2b), from the mains supply or a generator, where the direction of the current flow changes. The waveform of a current describes the shape of one cycle of the current.

Figure 2a Pulsed direct current (DC) (three cycles)	Figure 2b Alternating current (AC) (one cycle)

The frequency of a current is how many times one cycle of the waveform is repeated per second, and is measured in hertz (Hz). Mains electricity has a sine waveform (Figure 2b) and a frequency of 50Hz, i.e. it repeats 50 times per second. Higher frequency waveforms repeat more times per second; e.g. the frequency of the current in Figure 3a is four times the frequency of the current in Figure 3b.

Figure 3a Example of standard 200Hz frequency

Figure 3b Example of Standard 50Hz Frequency

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