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LESSON NOTE for

LESSON NOTE for. APPLIED ELECTRICITY. ALTERNATING CURRENT CIRCIUT THEORY 1. Generation of e.m.f in a single turn coil. POINTS. Alternating current is current which charges both in magnitude and direction uniformly in series of fluction .

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LESSON NOTE for

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  1. LESSON NOTE for APPLIED ELECTRICITY

  2. ALTERNATING CURRENT CIRCIUT THEORY 1 Generation of e.m.f in a single turn coil

  3. POINTS • Alternating current is current which charges both in magnitude and direction uniformly in series of fluction. • An e.m.f is generated in the coil, which varies in magnitude and reverses its direction at regular intervals.

  4. Definition of Terms • The WAVEFORM of e.m.f produced by an alternator is called a sine wave and the mains electricity supply if of “sinusoidal form”. • The CYCLE is the complete sequence of an alternating event. • The PERIOD (T) is the time taken for an alternating quantity to complete one cycle T = 1/F = 2π/ω

  5. Definition cont’d • The FREQUENCY (F) is the number of cycles completed in one second. Its unit is Hertz(Hz) • The Standard Frequency of the electricity supply in Nigeria is 50Hz. F = 1/T = ω/2π • Instantaneous values are the values of the alternating quantities at an instant of time. They are represented by small letters; j,v,a etc. • Peak Value, also known as amplitude or maximum value is the largest value reached in a half circle i.e. at the peak or crest of the waveform. Represented by capital letters; Q,P,R etc.

  6. Definition cont’d • A peak-to-peak value is the difference between the maximum and the minimum values in a cycle. • Average/Mean Value is the area under half cycle divided by the length of the base. It is = 0.637 × max. value • Effective Value is that current which will produce the same heating effect as an equivalent direct current. It is also called the root mean square (r.m.s) value. It is = 0.707 × max. value

  7. Definition cont’d • Form factor is the ratio of r.m.s value to the average value for any waveform i.e. form factor= r.m.s value/average value = 1.11 • Peak Value = max. value/r.m.s value = 1/0.707 = 1.41 = √2

  8. EVALUATION • What do you understand by the term A.C ? • Explain these terms as applied to A.C waveform • max. value • instantaneous values • r.m.s values

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