Exam 1: Introduction to Alternating Current

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Identify and explain the formula used to express the frequency of an ac generator.

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f = P X S/60
where
f = frequency, in hertz
P = number of pairs of poles
S = speed, in revolutions per minute (r/min)
60 = number of seconds in one minute

The use of ____________________'s generator rule shows that an alternating voltage is generated in the coil as it rotates.

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Fleming

Define alternating voltage.

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Alternating voltage may be defined as an electromotive force that changes continuously with time. It rises from zero to a maximum value in one direction and decreases back to zero. It then rises to the same maximum value in the opposite direction and again decreases to zero. These values are repeated again and again at equal intervals of time.

What is the advantage of using a higher-frequency?

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Most ac generators have ____________________ field windings.

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The amount of voltage induced in a conductor is proportional to what three factors?

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One ____________________ represents an amount of magnetic flux equal to 100,000,000 lines.

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A basic knowledge of trigonometry is essential to an understanding of alternating-current concepts.

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Traction motors require ____________________ current.

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In electronics, the frequencies used cover a very narrow range.

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Direct current is used for various electrochemical processes, including electroplating, refining of copper and aluminum, electrotyping, production of industrial gases by electrolysis, and charging of storage batteries.

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What is the definition of alternating current?

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Alternating-voltage waveforms are all sine waves.

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If the generator has two pairs of poles, then a cycle is generated every half-revolution, or 2 hertz per second.

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The commutators of dc generators are usually rated at less than ____________________ amperes (A).

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