nally measured in metres. that occur in one second and is therefore the reciprocal of the Equations 10.1 to 10.3 represent the relationships between veloc- periodic time. Frequency is measured in Hertz (Hz). ity, wavelength, time and frequency. The amplitude of the waveform represents the strength of the current at any instance, with the direction of the current, positive or Wavelength (10.1) Velocity = negative, being referred to as the polarity. The rotation of the wire loop within the magnetic field can be expressed in terms of rotation. The wire loop for each cycle will (10.2) move through 360 degrees. Figure 10.2 shows the sinusoidal wave- Frequency = Periodic time form plotted against angular rotation. Velocity = Wavelength X Frequency (10.3) 10.2.1 Waveshapes All component waveforms are made of a sinusoidal waveform which has a certain frequency, called the fundamental frequency Angular rotation and a number of other sinusoidal waveforms having frequencies that (degrees) are direct multiples of the fundamental frequency. These direct multiples are harmonics of the fundamental frequencies. For a complex waveform having a fundamental frequency, f, the harmonics with multiple values of f (e.g. 2f, 3f, 4f, etc.) may also be present. The square waveform is made of a fundamental frequency and all the odd harmonics rising to infinity, i.e. 3f, 5f, 7f, 9f, and SO on Figure 10.4 shows the square waveform with the associated Figure 10.2 Angular rotation At the same point in each cycle the amplitude of the waveform has the same value. The identification of a particular point in the cycle as the degree of rotation is called the phase of the alternating current waveform. Phase difference Waveform A Waveform B Space Figure 10.4 Square waveform Degrees (phase) terminology of space and mark. The amplitude of the various harmonics are added to give a resultant waveshape that approximates to a square wave. The addi- tion of the fundamental with the 3rd and 5th harmonics is illustrated in Figure 10.5. A more exact square wav