Page 253 - Basic Electrical Engineering

6. Draw the V–I characteristics of a variable resistor whose value of resistance has been fixed at
5 Ω, 8 Ω, and 10 Ω.
7. Explain the effect of change of temperature on the resistance of most of the conducting
materials.
8. What is meant by superconducting materials?
9. Prove that R = R (1+α t) for a conducting material where R is the resistance at t°C, R is the
t
0
t
0
0
resistance at 0°C, α is the temperature coefficient of resistance at 0°C and t is the rise in
0
temperature.
10. If α and α are the temperature coefficients of resistance at t and t degrees, respectively,
2
1
1
2
then prove that

11. Explain why resistance of most of the conducting materials increase with temperature.
12. From the definition of power as rate of doing work, show that power in an electric circuit

P = VI Watts

13. Distinguish between work, power, and energy.
14. Establish the relationship between resistance, current, voltage, power, and energy in an
electric circuit.
15. Show that 1 kWh is equal to 860 kilo Calories.
16. What is meant by a constant voltage source and a constant current source?
17. State with example the current divider rule and the voltage divider rule as applicable to
parallel circuits and series circuits, respectively.
18. State Kirchhoff’s current law and Kirchhoff’s voltage law.
19. What is Cramer’s Rule?
20. State and explain Thevenin’s theorem.
21. With a simple example show how, by applying Thevenin’s theorem, current flowing through
any branch of an electrical network can be calculated.
22. Write the steps of application of Thevenin’s theorem.
23. State and explain Norton’s theorem.
24. Distinguish between Thevenin’s theorem and Norton’s theorem.
25. What is maximum power transfer theorem? Prove the theorem.
26. Write the relationship of star–delta transformation of three resistors.
27. Distinguish between an ideal voltage source and a practical voltage source.
28. Write the conversion formula for delta to star conversion of three resistors.
29. What is the relationship between power, torque, and speed?
30. What are the limitations of Ohm’s law? Is Ohm’s law applicable in both dc and ac circuit?
31. State two fundamental laws of circuit analysis.
32. What is meant by time constant of an R–L circuit?
33. Derive equations that relate the resistance of a material at two different temperatures.
34. If n number of resistances each of value R are connected in parallel, then what will be the
value of their equivalent resistance?