Page 411 - Basic Electrical Engineering

3.4 REVIEW QUESTIONS

A. Short Answer Type Questions

1. Explain frequency, time period, instantaneous value, maximum value, and average value for a
sinusoidal voltage.
2. What do you understand by harmonic waves of a non-sinusoidal wave?
3. Why do we use RMS value instead of average value for an alternating quantity?
4. Show that for a sinusoidal voltage, RMS value is 0.707 times its maximum value.
5. What is the value of form factor for a sine wave? What is the significance of the value of form
factor for an alternating quantity?
6. The form factors for different kinds of voltage wave shapes have been calculated as 1.0, 1.11,
and 1.15. Is it possible to predict the type of the voltage wave shapes?
7. What is inductive reactance, capacitive reactance, and impedance of an L–R–C circuit?
8. What is meant by power factor of an ac circuit? What is its minimum value and its maximum
value?
9. Prove that average power in an ac circuit is ϕ where V is the RMS value of voltage, I is the
RMS value of current, and ϕ the power factor.
10. What is the significance of very low (poor) power factor of a circuit?
11. A resistance R, an inductance L, and a capacitance C are connected in series across an
alternating voltage, V. A current I flows through the circuit. Draw a phasor diagram showing
the voltage drops across the circuit parameters with respect to V and I.
12. A resistance of 10 Ω and an inductive reactance of 10 Ω are connected in series. Calculate the
value of impedance and draw the impedance triangle.
13. Show that current in a pure inductive circuit lags the voltage by 90°.
14. What is the power factor of a purely resistive circuit, purely inductive circuit, and purely
capacitive circuit?
15. State the condition for maximum current in an L–R–C series circuit.
16. State the condition for series resonance in an L–R–C circuit.
17. State the condition for parallel resonance. How do we calculate the value of capacitor to be
shunted to create a resonant condition?
18. What is the value of resonant frequency in the case of series resonance and in the case of
parallel resonance?
19. What is meant by Q-factor of a series resonant circuit? What does Q-factor signify?
20. What do you mean by bandwidth in a series circuit?
21. A resonant circuit with high Q-factor is also called a tuned circuits. Explain why.
22. Write the expression for resonant frequency, Q-factor, and dynamic impedance for a parallel
resonant circuit.