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Saturday, 26 September 2015

Basic Concepts of Electricity - Multiple Choice Questions

Basic Concepts of Electricity - Multiple Choice Questions Points : basic concepts of electricity multiple choice questions and answers, electrical objective type question answers, mcqs 1. Electric current in a liquid is due to the flow of
(i) electrons only a
(ii) positive ions only
(iii) Negative and positive ions both
(iv) electrons and positive, ions both

2. If number of valence electrons of an atom is more than 4, the substance is usually
(i) a semiconductor
(ii) a conductor
(iii) an insulator
(iv) none of the above.

3. One coulomb of charge is equal to charge on
(i) 625 x 1016 electrons
(ii) 6.25 x 1016 electrons
(iii) 62.5 x 1016 electrons
(iv) 0.625 x 105 electrons

4. Diameter of an atom is about
(i) 10-10m
(ii) 10-8m
(iii) 10-2m
(iv) 10-15m

5. Electrons in the last orbit of an atom are called
(i) free electrons
(ii) bound electrons
(iii) valence electrons
(iv) thermionic electrons

6. If number of valence electrons of an atom is less than 4, substance is generally
(i) a conductor
(ii) an insulator
(iii) a semiconductor
(iv) none of the above

7. If number of valence electrons of an atom is 4, then the substance is generally
(i) a semiconductor
(ii) an insulator
(iii) a conductor
(iv) none of the above

8. Mass of a proton is ..... the mass of electron.
(i) equal to
(ii) less than
(iii) about 1837 times
(iv) 200 times

9. Number of compounds available in nature is
(i) 105
(ii) 300
(iii) 1000
(iv) unlimited

10. E.M.F. in a circuit
(i) increases circuit resistance
(ii) decreases circuit resistance
(iii) maintains potential difference
(iv) none of the above

11. 1 cm3 of copper at room temperature has about
(i) 200 free electrons
(ii) 20 x 1010 free electrons
(iii) 8.5 x 1022 free electrons
(iv) 3 x 105 free electrons

12. Electric current is due to the flow of
(i) positive charges only
(ii) negative charges only
(iii) both positive and negative charges
(iv) neutral particles only

13. Electric current in a metallic conductor is due to the flow of
(i) electrons only
(ii) positive ions only
(iii) electrons and positive ions only
(iv) neutral atoms Only

14. Electric current is a
(i) scalar quantity
(ii) vector quantity
(iii) sometimes scalar and sometimes vector
(iv) number on

15. Potential difference has he unit of
(i) charge
(ii) power
(ii) energy
(iv) none of the above

16. Billion electron pass through a cross-section of a conductors in 10-3s. The current is
(i) 10-7 A
(ii) 16 x 10-7 A
(iii) 2 x 10-4 A
(iv)26 x 10-3 A

17. Specific resistance of a wire depends
(i) its length
(ii) its cross-sectional area
(iii) its dimensions
(iv) its material

18. Electric current in a discharge tube containing a gas is due to.
(i) electrons only
(ii) positive ions only
(ii) negative and positive ions both
(iv) electrons and positive ions, both

19. How long does it take 50 μc of charge to pass a point in a circuit if current flow is 15 mA ?
(i) 3.33 x 10-3
(ii) 6 x 102 s
(iii) 2s
(iv) none of the above

20. Length of wire has a resistance of 6 ohms. The resistance of a wire of the same material three times as long and twice the cross-sectional area will be.
(i) 36 ohms
(ii) 9 ohms
(iii) 1ohm
(iv) 12 ohms

21. Quantity of charge that will be transferred by a current flow of 10 A over 1 hour period is
(i) 10 C
(ii) 3.6 x 104 C
(ii) 2.4’x 103C
(iv) 1.6x 102C

22. Resistance of a straight conductor is independent of
(i) temperature
(ii) material
(iii) cross-sectional area
(iv) shape of cross-section

23. Conductivity is reciprocal of
(i) current density
(ii) resistance
(iii) resistivity
(iv) none of the above

24. Drift velocity of electrons is of the order of
(i) 1ms-1
(ii) 10-3 ms-1
(iii) 106 ms-1
(iv) 3 x 10 ms-1

25. Potential difference of an energy source that. provides 50 mJ bf energy for every micro coulomb of charge that flows is
(i) 5V
(ii) 50 V
(iii) 500 V
(iv) 50kV

26. Semiconductors have ........ temperature coefficient of resistance
(i) zero
(ii) negative
(iii) positive
(iv) none of the above

27. Specific resistance of a metallic conductor ........ with rise in temperature
(i) increases
(ii) decreases
(iii) remains unchanged
(iv) none of the above

28. Insulators have ................. temperature coefficient of resistance
(i) zero
(ii) positive
(iii) negative
(iv) none of above

29. What amount of charge must be delivered by a battery with a potential difference of 100 V to do 500 J of work?
(i) 5C
(ii) 0.5C
(iii) 50 C
(iv) 500 C

30. Eureka has temperature co-efficient of resistance.
(i) almost zero
(ii) negative
(iii) positive
(iv) none of the above

31. Piece of aluminium wire is stretched to reduce its diameter to half of its original value. Its resistance will become
(i) two times
(ii) four times
(iii) eight times
(iv) sixteen times

32. SI unit of conductivity is
(i) ohm-m
(ii) ohm/m
(iii) mho-m
(iv) mho/m

33. Piece of aluminium (A1) and germanium (Ge) are called from T1 K to T2 K. The resistance of
(i) each of them increases
(ii) each of them decreases
(iii) aluminium increases and that of germanium decreases
(iv) aluminium decreases and that of germanium increases

34. Constantan wire is use for creation standard resistance as it has
(i) low specific resistance
(ii) high specific resistance
(iii) negligibly small temperature co-efficient of resistance
(iv) high melting point

35. Resistivity of a material is 2 x 10-8Ώ m. What will be the resistance of a hollow pipe of the material of length 1 m and having inner and outer radii 10 cm and 20 cm respectively?
(i) 2x 1O-4 Ω
(ii) 21 x 10-7 Ω
(iii) 3 x 10-5 Ω
(iv) 2.82 x 10-3 Ω

36. Value of a (temperature co-efficient of resistance) depends upon
(i) length of the material
(ii) X-sectional area of the material
(iii) volume of the material
(iv) nature of the material and temperature

37. At 0 K, germanium behaves as
(i) a conductor
(ii) an insulator
(iii) a superconductor
(iv) a ferromagnetic substance

38. Example of non-ohmic resistance is
(i) copper wire
(ii) carbon resistance
(iii) aluminium wire
(iv) tungsten wire

39. Which one of following is the finest conductor of electricity?
(i) silver
(ii) gold
(iii) copper
(iv) zinc

40. As temperature of a metallic resistor is enlarged, the product of its resistivity and conductivity
(i) increases
(ii) decreases
(iii) remains constant
(iv) may increase or decrease

41. Resistance of human body is about
(i) 200Ω
(ii) 10Ω
(iii) 1000Ω
(iv) 25Ω

42. Specific resistance of material of wire depends on
(i) the area of cross-section
(ii) length
(iii)mass
(iv) none of the above

43. Copper wire is extended so that its length is increased by 0.1%. Change in its resistance is
(i) 0.3 %
(ii) 0.4 %
(iii) 0.2 %
(iv) none of the above

44. If an electric current is conceded through a nerve, the man
(i) begins to laugh
(ii) begins to weep
(iii) is excited
(iv) becomes insensitive to pain

45. Ampere - hour is unit of
(i) quantity of electricity
(ii) strength of current
(iii) power
(iv) energy

46. Which of following is the finest material for making linking wires?
(i) manganin
(ii) constantan
(iii) copper
(iv) nichrome

47. In which of following substances resistance decreases by enlarge in temperature?
(i) carbon
(ii) constantan
(iii) copper
(iv) silver

48. The hot resistance of electric bulbs filament is higher than its cold resistance as the temperature co-efficient of filament is
(i) zero
(ii) positive
(iii) negative
(iv) none of above

49. Ampere second is unit of
(i) power
(ii) energy
(iii) emf
(iv) charge

50. Current in a circuit have stable resistance is tripled. The power increases
(i) 1/9 times
(ii) 3 times
(iii) 9 times
(iv) 1/3 times

51. No current flows among two charged bodies if they have similar
(i) capacity
(ii) potential
(iii) charge
(iv) none of the above

52. An electric heater is clear 2000 W , 200 V. The resistance of coil is
(i) 0.1 Ω
(ii) 20 Ω
(iii) 1/20 Ω
(iv) 200 Ω

53. The filament of an electric bulb is prepared of
(i) tungsten
(ii) nickel
(iii) steel
(iv) aluminium

54. Percentage by which the incandescence of lamp decreases due to drop of current through 3% is
(i) 6%
(ii) 3%
(iii) 9 %
(iv) 12 %

55. Wire having extremely high value of conductance is said to be
(i) very good conductor
(ii) moderately good conductor
(iii) insulator
(iv) none of the above

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