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| 3. If a conductor that 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 an induced electromotive force (EMF). The EMF depends on the strength of the magnetic field, the length of the conductor, and the speed with which the conductor cuts the magnetic field. |

| 4. When a coil or loop is turned within a magnetic field, a voltage will be produced which will rise from zero to maximum, back to zero, then to a maximum in the opposite direction and back to zero (Fig. 1-7). The voltage thus induced will produce an alternating current (ac) in the coil or loop (Fig. 1-8). |

| 5. A conductor carrying alternating current will produce an alternating magnetic field around it; if another conductor parallels it closely, another ac voltage will be produced in it by the alternating magnetic field of the first conductor cutting it (Fig. 1-11). |

| 6. If two coils are wrapped around a common iron or steel core, an ac voltage in one will produce an ac voltage in the other. The ratio of these voltages will be the same as the ratio of the number of turns in the coils (Fig. 1-16). This assembly of coils and core constitutes a transformer (Fig. 1-14). The input coil is usually called the primary and the output coil the secondary. |

| 7. Losses developed in the transformer are given off as heat. The rating of a transformer is usually limited by how hot it is allowed to become. It is rated in kilovolt-amperes or kVA (Fig. 1-18). |

| STUDY QUESTIONS |

| 1. What is a transformer and what does it do? |

| 2. What general relationship exists between the input and output of a transformer? |

| 3. What two effects are produced when a current of electricity flows through a wire? |

| 4. How may a voltage be induced in a conductor? What factors affect its magnitude? |

| 5. How is a voltage generated in a coil of the transformer? What is the relationship between the input or primary voltage and the output or secondary voltage? |

| 6. What is meant by the ratio of transformation or turns ratio? |

| 7. Describe the action of a transformer when a load is connected to the secondary. |

| 8. What are the energy losses in a transformer? What form do they take? |

| 9. What is meant by the regulation of a transformer? What factors affect it? |

| 10. How are transformers' ratings expressed? What limits their capacity? |

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