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| the magnetic field is increased, it is found that the voltage induced in the conductor is also increased. The magnitude of the electrical pressure induced in a conductor while it is moving through a magnetic field, therefore, is determined by the rate of cutting of the lines of force of the magnetic field. |

| If a conductor which is part of a closed circuit is moved through a magnetic field, an electric current will flow in the conductor. The current results from what is called the induced electromotive force (EMF). But this happens only if the directions (1) of the current, (2) of the magnetic field, and (3) of the motion are at right angles to each other. |

| If a loop of wire (as illustrated in Fig. 1-7) is rotated at uniform speed in a magnetic field, a voltage is induced in the conductor that makes up the loop. If the voltage for different positions of the loop is measured and the angular position of the loop, (in Fig. 1-7) the waveform of the induced voltage can be obtained. This waveform is called a sine wave. Note that the instantaneous values of the voltage changes continuously from zero to maximum, from maximum back to zero, from zero to a maximum in the opposite direction, and then back to zero, thus completing one cycle. The maximums, in either direction of the voltage wave are called the amplitude of the voltage, and the number of cycles per second the frequency of the wave. The part of the curve from zero-to-maximum-back-to-zero is called an alternation. Such a waveform is an example of the form of voltage and current in the alternating current circuit. |

| Figure 1-7 Sine-wave voltage induced in coil as it rotates in magnetic field. |

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