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Page 6

| How It Works: Electromagnetism |

| In order to describe how the transformer works, it is necessary to review briefly some simple elements of electricity. |

| Electromagnetic Fields. |

| A current of electricity flowing through a wire produces not only heat, but also a magnetic field about the wire. This may be proved by placing a compass in the vicinity of the current-carrying conductor. (Fig. 1-3.) |

| Figure 1-3 Magnetic field around a conductor. |

| The magnetic field around a single wire carrying a current may be rather weak. By winding the wire into a ring, the magnetic lines of force (sometimes called magnetic flux), are concentrated in the small space inside the coil and the magnetic effect is much increased. (Fig. 1-4.) The grouping of the lines of force is known as a magnetic field. |

| A coil of wire is nothing but a succession of these rings stacked one after the other (Fig. 1-5A). Each adds its quota to the magnetic field. Most of the magnetic lines of force pass straight through the coil. Each line makes a complete circuit, returning by a path outside the coil. A coil carrying a current is in fact a magnet. Where the lines come out is referred to (for identification) as the north (N) pole, where they enter as the south (S) pole (Fig. 1-5B). |

| Figure 1-4 Magnetic field about a wire loop. |

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