Basic Electrical Electronics Viva Short Questions and Answers PDF

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1.State Ohm’s law. 
Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference or voltage across the two points, and inversely proportional to the resistance between them. The mathematical equation that describes this relationship is:
V =
I R I is the current through the resistance in units of amperes, V is the potential difference measured across the resistance in units of volts, and R is the resistance of the conductor in units of ohms. Ohm's law states that the R in this relation is constant, <PDF Download>

2. State Kirchhoff’s voltage law. 
In any closed circuit or mesh, the algebraic sum of all the electromotive forces and the voltage drops is equal to zero. 

3. State Kirchhoff’s Current law. 
The sum of the currents flowing towards any junction in an electric circuit equal to the sum of currents flowing away from the junction. 

4. Mention the limitations of Ohm’s Law. 
5. State two salient points of a series combination of resistance. 
6. State two salient points of a parallel combination of resistance. 
7. Give two applications of both series and parallel combination. 
8. Define an ideal voltage source. 
9. Define an ideal current source. 
10. Explain how voltage source with a source resistance can be converted into an equivalent current source. 11. Define R.M.S value. 
12. State the advantages of sinusoidal alternating 
13. Mention the two types of MI instruments. 
14. How can ammeter and voltmeter are connected in a circuit? Why?

1. State and explain Kirchoff’s law. (8) (b) Explain the working of a Dynamometer wattmeter with a neat sketch. (8) 
2. (a) Explain any one type of MI instruments. (8) (b) Explain the working principle of PMMC instruments. (8) 
3. Explain the construction and principle of operation of single phase energy meter. (16) 
4. (a) A series circuit has R=10ohm, L=50mH, and C=100μF and is supplied with 200V,50Hz. Find (i) Impedance (ii) current (iii) power (iv) power factor (v) voltage drop across the each element. (8) (b) Derive the equation for equivalent resistance of number of resistors connected in parallel. (8)
5. A 400V is applied to three star connected identical impedances each consisting of a 40 ohm resistance in series with 3ohm inductance reactance. Find (i) line current (ii) Total power supplied. (16)

1.State the three basic types of rotating electrical machines. 
2. State two types of induction motors. 
3. Mention the difference between core and shell type transformers. 
4. What is the purpose of laminating the core in a transformer?
5 .Write down the emf equation for d.c.generator. 
6. Does transformer draw any current when secondary is open? Why? 
7. Define voltage regulation of a transformer. 
8. What are the applications of step-up & step-down transformer? 
9. .Give the emf equation of a transformer and define each term. 
10. How transformers are classified according to their construction? 
11. Why the armature core in d.c machines is constructed with laminated steel sheets
instead of solid steel sheets? 
12. Why commutator is employed in d.c.machines? 

13. What is the function of capacitor in a single phase induction motor? 

14. How does d.c. motor differ from d.c. generator in construction? 

15. How will you change the direction of rotation of d.c.motor? 

16. What happens when the centrifugal switch fails to close?

1. Explain the construction and principle of operation of a DC generator with neat sketch. (16) 
2. (a) Derive the equation for induced EMF of a DC machine. (8) (b) Derive the torque equation of DC motor. (8) 
3. A 25kw, 250V, dc shunt generator has armature and field resistances of 0.06ohm and 100ohm respectively. Determine the total armature power developed when working (1) as a generator delivering 25 kW output and (2) as a motor taking 25kw. (16) 
4. (a) Derive the EMF equation of a transformer. (8) (b) Explain the principle of operation of DC Motor. (8) 
5. Explain the construction and principle of operation of single phase induction motor. (16) 
6. A transformer with 40 turns on the high voltage winding is used to step down the voltage from 240V to 120V. Find the number of turns in the low voltage winding. (16) 
7. Describe the construction details of transformer and also explain the principle of operation.(16)

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