Basic Electrical Engineering MCQ

1. Ohm’s law cannot be applied to the circuits consisting of

(a) electronic tubes or transistors
(b) non-linear elements
(c) powdered iron, electric arc etc.
(d) all of the above.

An electric circuit, whose characteristics or properties are same in either direction (e.g. a distribution or transmission line) is called the bilateral circuit.

An electric circuit, whose characteristics or properties change with the direction of operation (e.g. a diode rectifier) is called the unilateral circuit.

Circuit elements, who don’t have linear relationship between voltage and current are called non-linear elements (e.g. powdered iron, electric arc).

The Ohm’s law cannot be applied to unilateral circuits and non-linear elements.

2. If the length of a wire of resistance R is uniformly stretched to n times its original value, what will be its new resistance?

(a) n²R
(b) nR
(c) n/R
(d) nR²

Answer: (a) n²R

3. An electric current is the

(a) random movements of electrons in a conductor
(b) movement of free electrons prominently in one direction
(c) pressure difference between two poles
(d) the power that causes drift of electrons

4. In gases the flow of current is due to

(a) electrons only
(b) positive and negative ions
(c) electrons and positive ions
(d) electrons, positive ions and negative ions

5. The minimum requirements for causing flow of current are

(a) a voltage source, a resistor and a switch
(b) a voltage source and a conductor
(c) a power source and a bulb
(d) a voltage source, a conductor, an ammeter and a switch

6. Current velocity through a copper conductor is

(a) nearly 3 x 10⁹ m/s
(b) in the order of a few µm/s
(c) independent of current strength
(d) the same as propagation velocity of electric energy

7. The drift velocity of electrons is

(a) larger than speed of light
(b) almost equal to speed of light
(c) equal to speed of light
(d) very small in comparison to speed of light

8. Correct form of Ohm’s law is

(a) I = VR
(b) V α I
(c) V = IR
(d) above (b) and (c)

9. The condition for the validity of ohm’s law is that the

(a) temperature should remain constant
(b) current should be proportional to voltage
(c) resistance must be wire wound type
(d) all of the above

10. Ohm’s law is applicable to

(a) semiconductors
(b) vacuum tubes
(c) electrolytes
(d) carbon resistors
(e) arc lamps
(f) none of these

11. The electrical conductivity of metals is typically of the order of (in ohm^-1m^-1)

(a) 10⁷
(b) 10⁵
(c) 10^-4
(d) 10^-6

12. Resistance of a copper wire always increases if

(a) temperature is reduced
(b) temperature is increased
(c) number of free electrons becomes less
(d) number of free electrons becomes more

13. Pure metals generally have

(a) high conductivity and low temperature coefficient
(b) high conductivity and large temperature coefficient
(c) low conductivity and zero temperature coefficient
(d) low conductivity and high temperature coefficient

14. Specific resistance of a conductor depends upon

(a) dimensions of the conductor
(b) composition of the conductor material
(c) resistance of the conductor
(d) both (a) and (b)

15. The insulation resistance of a cable of length 10 km is 1 mega-ohm, for a length of 100 km of the same cable, the insulation resistance will be

(a) 1 mega-ohm
(b) 10 mega-ohm
(c) 0.1 mega-ohm
(d) 0.01 mega-ohm

16. The temperature coefficient of resistance of an insulator is

(a) positive and independent of temperature
(b) negative and independent of temperature
(c) negative and dependent of temperature
(d) positive and dependent of temperature

17. To determine the polarity of the voltage drop across a resistor, it is necessary to know the

(a) value of resistor
(b) value of current
(c) direction of current flowing through the resistor
(d) value of EMF in the circuit

18. Kirchhoff’s laws are valid for

(a) linear circuits only
(b) passive time invariant circuits
(c) non-linear circuits
(d) both linear and non-linear circuits

19. Kirchhoff’s laws are not applicable to circuits with

(a) distributed parameters
(b) lumped parameters
(c) passive elements
(d) non-linear resistance

20. Superposition theorem is not applicable for

(a) voltage calculations
(b) bilateral elements
(c) power calculation
(d) passive elements

21. Which of the following theorems is applicable for both linear and non-linear circuits?

(a) Superposition
(b) Thevenin’s
(c) Norton’s
(d) none of these

22. Superposition theorem is applicable for

(a) linear circuits only
(b) non-linear circuits only
(c) linear circuits and non-linear circuits both
(d) none of these.

23. While Thevenizing a circuit between two terminals, V_TH is equal to

(a) short-circuit terminal voltage
(b) open-circuit terminal voltage
(c) net voltage available in the circuit
(d) EMF of the battery nearest to the terminals

24. While determining R_TH of a circuit

(a) voltage and current sources should be left as they are
(b) all sources should be replaced by their source resistances
(c) all independent current and voltage sources are short-circuited

25. In a balanced Wheatstone bridge, if the position of detector and source are interchanged, the bridge will still remain balanced. This inference can be drawn from

(a) Reciprocity theorem
(b) Duality theorem
(c) Compensation theorem
(d) Equivalence theorem

26. An ideal voltage source will charge and ideal capacitor

(a) in infinite time
(b) exponentially
(c) instantaneously
(d) none or the above

27. To prevent the generation of static charge on rubber or flat leather

(a) surface is moistened
(b) conductive dressing is done
(c) oil compound dressing is done
(d) any of the above

28. To remove static charge from a machine the

(a) machine is insulated
(b) insulated cabins are constructed
(c) framework is earthed
(d) any of the above

29. While testing a capacitor with ohmmeter, if the capacitor shows charging but the final resistance reading is appreciably less than the normal. The capacitor is

(a) leaky
(b) open circuited
(c) short circuited
(d) satisfactory

30. While testing a capacitor with ohmmeter, if the capacitor shows practically zero reading. The capacitor is

(a) leaky
(b) short circuited
(c) open circuited
(d) satisfactory

31. While testing a good 0.05 MFD capacitor with ohmmeter, the meter will show

(a) high resistance momentarily and then a very low resistance.
(b) low resistance momentarily and then a very high resistance.
(c) a reading of 70 ohm.
(d) none of the above.

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