ALTERNATING CURRENT (5 marks & 3 marks)

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  1. Describe the principle construction and working of an AC generator. Draw neat labeled diagram
  2. Define mean value of AC(over a half cycle) and derive an expression for it.
  3. Define RMS value of AC and derive an expression for it. ()
  4. Show that the average value of AC over a complete cycle is zero.
  5. Show that the current and voltage are in phase in an ac circuit containing resistance only.
  6. Deduce the phase relationship between current and voltage in an ac circuit containing inductor only.
  7. Deduce the phase relationship between current and voltage in an ac circuit containing capacitor only.
  8. Draw the phasor diagram showing voltage and current in LCR series circuit and derive an expression for the impedance
  9. What do you mean by resonance in Series LCR circuit? Derive an expression for the frequency of resonance in LCR circuit.
  10. Distinguish between resistance, reactance and impedance.
  11. Define quality factor (Q factor) of resonance and derive an expression for it.
  12. Describe the mechanism of electromagnetic oscuillations in LC circuit and write expression for the frequency of oscillations produced.
  13. Derive an expression for the average power in an ac circuit.
  14. Define power factor. Deduce expression for it and explain wattless current?
  15. Describe the principle construction theory and working of a transformer.
  16. Describe the various losses in a transformer and explain how the losses can be minimised.

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