Sample Question and Answer for FEEE Lab Viva-voce

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1. What should be the internal resistance of a practical voltmeter? Ans : Very high
2. What should be the internal resistance of a ideal voltmeter? Ans : Infinity
3. What should be the internal resistance of a practical ammeter? Ans : Very low
4. What should be the internal resistance of a ideal ammeter? Ans : Zero
5. Voltmeter should be connected in ____ with load? Ans : Parallel or shunt
6. Ammeter should be connected in ____ with load? Ans : Series
7. How many coils are there in a Wattmeter? Ans : 2, Current coil and Pressure or Voltage coil
8. How many terminals are there in a Wattmeter? Ans : 4, M (Main line), C (Common), L (Load), V (Voltage or Neutral)
9. What is multiplying factor of Wattmeter? Ans : It is the ratio of (Voltage range X Current range) / full scale deflection of the wattmeter.
10. Which kind resistive load you have used in experiment? Ans : Rheostat and Incandescent Lamp
11. What is Variac? Ans: It is an Auto-transformer, which is used to get variable ac voltage from 0 to 270 Volt.
12. SI unit of Power? Ans : Watt
13. SI unit of Voltage? Ans : Volt
14. SI unit of Current? Ans : Ampere
15. SI unit of power factor? Ans : Unitless
16. SI unit of frequency? Ans : Hertz
17. SI unit of resistance, inductive reactance, capacitive reactance, impedance? Ans : Ohm
18. SI unit of inductance? Ans : Henry
19. SI unit of capacitance? Ans : Farad
20. What is power factor? Ans : It is the ratio of active power (VIcos phi) to the apparent power (VI) or we can say, it is the ratio of kW/kVA or it is the ratio of resistance (R) to the impedance (Z)
21. What is the power factor of Inductive load? Ans : Lagging
22. What is the power factor of Capacitive load? Ans : Leading
23. What is the power factor of Resistive load? Ans : Unity
24. How many terminals are there in a Power factor meter? Ans : 4, M (Main line), C (Common), L (Load), V (Voltage or Neutral)
25. What is the range of a power factor meter? Ans : 0.5 lag to unity to 0.5 lead
26. What kind of inductive load you have used in experiment? Ans : Choke of Fluorescent Tube
27. Which parts you have seen in a transformer? Ans : Laminated core, Primary winding, Secondary winding, terminals
28. Why the core is laminated? Ans : To reduce eddy current loss
29. Core is made of which material and why? Ans : Silicon Steel, to reduce hysteresis loss
30. What is primary winding? Ans : The winding, which is connected with input power supply.
31. What is secondary winding? Ans : The winding, from where we take output power.
32. On which principle a transformer works? Ans : Mutual induction
33. What is transformation ratio? Ans : It is the ratio of secondary voltage to primary voltage or secondary number of turns to the primary number of turns or primary current to the secondary current
34. What colors can be found in an 1 ohm resistor? Ans : Brown, Black, Golden and Golden or Silver as per tolerance
35. What colors can be found in an 100 +- 5% ohm resistor? Ans : Brown, Black, Brown and Golden
36. What is tolerance? Ans : It is the limit of a resistor, that the value of the resistor may vary.
37. What is forward bias of a diode? Ans : If the +ve terminal or anode of a diode is connected with +ve side of souce and cathod or -ve terminal of the diode is connected with -ve side of the souce, then the bias is, forward bias.
38. What is reverse bias of a diode? Ans : If the +ve terminal or anode of a diode is connected with -ve side of souce and cathod or -ve terminal of the diode is connected with +ve side of the souce, then the bias is, reverse bias.
39. How do you identify the terminals of a diode? Ans : By looking at the silver ring. The side of silver ring indicates the cathod (-ve) terminal and the the other side indicates the anode (+ve) terminal.
40. What is the knee voltage of silicon diode and germanium diode? Ans : 0.7 V for silicon diode and 0.3 V for germanium diode.