Electro Magnetism

13 mins read

1. The purpose of choke in a fluorescent lamp is –
(A) To decrease the voltage momentarily
(B) To increase the flow of current
(C) To decrease the resistance
(D) To decrease the flow of current
Ans. (D)

2. The cause of magnetism in materials is–
(A) Electrons at rest (B) Protons at rest
(C) All stationary neutrons
(D) Circular motion of electrons.
Ans. (D)

3. Uniform magnetic field is represented by–
(A) Closed curves (B) Parallel lines
(C) Convergent lines (D) Divergent lines
Ans. (B)

4. What is the unit of electrical conductivity?
(A) Ohm (B) Ohm-cu
(C) Mho (D) Ohm/cu
Ans. (C)

5. Who discovered the link between electricity and magnetism?
(A) Maxwell (B) Diesel
(C) Michael Faraday (D) Volta
Ans. (C)

6. Tesla is the unit of Magnetic field –
(A) Induction (B) Moment
(C) Area (D) Flow
Ans. (A)

7. Resistance of a conductor increases on –
(A) Increasing Length
(B) Decreasing area of cross–section
(C) Increasing temperature (D) All of these
Ans. (D)

8. Which of the following rated electric bulb?
(A) Power and current
(B) Power and voltage
(C) Current and voltage
(D) Energy and current
Ans. (B)

9. Chemical Energy is converted into Electric Energy–
(A) Dynamo (B) Electric Fan
(C) Battery (D) Atom Bomb
Ans. (C)

10. Certain Substances loses their electrical
resistance completely at super low temperatures
such substances are called.–
(A) Superconductor (B) Semiconductor
(C) Dielectric (D) Perfect conductor
Ans. (A)

11. The substance having inf inite electric
resistance are called –
(A) Conductor (B) Insulator
(C) Resistor (D) Electrolyte
Ans. (B)

12. What is the conductivity of super conductor?
(A) Zero (B) Infinite
(C) Less (D) More
Ans. (B)

13. What is the resistance of an ideal voltmeter?
(A) Infinite (B) Zero
(C) High (D) Low
Ans. (A)

14. Magnetic keeper are the pieces of –
(A) Nickel (B) Cobalt
(C) Iron (D) Soft Iron
Ans. (D)

15. Device used to convert A.C. into D.C. known as–
(A) Dynamo (B) Inductive coil
(C) Generator (D) Rectifier
Ans. (D)

16. The Solids which conducts the electricity at
high temperature but not at low temperature are called–
(A) Super conductor (B) Semiconductor
(C) Metallic conductor (D) Insulator
Ans. (B)

17. Which of the following is a conductor of electricity?
(A) Rubber (B) Pure water
(C) Salt water (D) Benzene
Ans. (C)

18. The metal used in wires at domestic Level –
(A) Nickel (B) Aluminium
(C) Iron (D) Copper
Ans. (D)

19. Fuse wire used as a safety device in domestic
electrical appliances is made up of metal having–
(A) Low resistance (B) Low melting point
(C) Low conductivity (D) Low specific gravity
Ans. (B)

20. For which of the following ohm’s law is
correctly applicable?
(A) Insulator (B) Semi conductor
(C) Conductor (D) Super conductor
Ans. (C)

21. When number of turns in a coil are made thrice
without any change in the length of coil, then
what will be its self inductance?
(A) Three times (B) Nine times
(C) Six times (D) One-third
Ans. (B)

22. If a wire of Resistance ‘R’ is melted and recast
to half of its Length, then the new resistance
of the wire will be–
(A) R/4 (B) R/2
(C) R (D) 2R
Ans. (A)

23. During electro refining, Pure Metal is collected at–
(A) Anode (B) Cathode
(C) Container (D) Electrolyte
Ans. (B)

24. Which of the following is an electrolytic conductor–
(A) Iron (B) Gas carbon
(C) Copper Sulphate (D) Mercury
Ans. (C)

25. Which of the following is best conductor of electricity?
(A) Copper (B) Iron
(C) Aluminium (D) Silver
Ans. (D)

26. During the conduction of current, conductor becomes–
(A) Positively charged (B) Negatively charged
(C) Electrically neutral
(D) Alternatively positively and negatively charged
Ans. (C)

27. Current carrying conductor is related to –
(A) Magnetic Field (B) Electric Field
(C) Electro Magnetic Field(D) Electrostatic Field
Ans. (A)

28. A Conducting wire is –
(A) Positively Charged
(B) Negatively Charged
(C) Neutral
(D) Charged depending upon the power of current
Ans. (C)

29. The process of connecting of wires is called –
(A) Catenation (B) Combination
(C) Cohesion (D) Addition
Ans. (B)

30. In the resistance color code, the fourth band signifies–
(A) Tolerance level (B) Power of ten
(C) Total value to resistance
(D) The material of the resistor
Ans. (A)

31. A piece of wire having Resistance ‘R’ is cut
into ‘n’ equal parts and then connected into
parallel combination what will be the effective
Resistance of combination?
(A) nR (B) R/n
(C) n/R (D) R/n²
Ans. (D)

32. Water should not be used to extinguish fire
caused by electricity, because –
(A) It may cause electrocution
(B) It may cause dissociation of water
(C) It may cause electric dissociation
(D) Fault may occour in wires
Ans. (A)

33. Metal used for the manufacturing of Lightning
conductor is –
(A) Iron (B) Aluminium
(C) Copper (D) Zinc
Ans. (C)

34. When two semiconductors of P and N-type are
brought in contact, they form p-n Junction which acts like a/an–
(A) Conductor (B) Rectifier
(C) Amplifier (D) Oscillator
Ans. (B)

35. Which of the following statements is incorrect
regarding the resistance of a wire?
(A) It depends upon the material of wire
(B) It is proportional to the length of wire
(C) It is proportional to the area of cross-section of wire
(D) On increasing temperature resistance of metal wire increases
Ans. (C)

36. We can find with the help of Galvanometer –
(A) Resistance (B) Energy
(C) Current (D) Temperature
Ans. (C)

37. Multimeter is used to measure the –
(A) Current (B) Voltage
(C) Resistance (D) All of these
Ans. (D)

38. In A.C. circuits A.C. meter measures –
(A) Mean value (B) Rms value
(C) Peak value (D) Root mean value
Ans. (B)

39. Which of the following instrument is used to measure the electric current?
(A) Ammeter (B) Voltmeter
(C) Wattmeter (D) Anemometer
Ans. (A)

40. S.I. Unit of electric charge is –
(A) Ampere (B) Coulomb
(C) ESU (D) Kelvin
Ans. (B)

41. Who discovered the battery?
(A) Faraday (B) Volta
(C) Maxwell (D) Roentgen
Ans. (B)

42. What is the unit of electric power?
(A) Watt (B) Volt
(C) KWH (D) Ampere
Ans. (A)

43. Alternating current is converted into direct current by using –
(A) Transformer (B) Dynamo
(C) Rectifier (D) Inverter
Ans. (C)

44. Fleming Right Hand Rule is used to find the direction of–
(A) Alternating current (B) Direct current
(C) Induced current (D) Original current
Ans. (C)

45. Instrument used to change the speed of electric fan –
(A) Amplifier (B) Regulator
(C) Switch (D) Rectifier
Ans. (B)

46. Best Liquid for the transformer core is–
(A) Stainless steel (B) Cast steel
(C) Hard steel (D) Soft iron
Ans. (D)

47. Transformer is used for –
(A) To increase the A.C. voltage
(B) To increase DC. Voltage
(C) To convert Electric Energy into heat energy
(D) To convert AC into DC.
Ans. (A)

48. The filament of the electric bulb is made up of–
(A) Copper (B) Nichrome
(C) Lead (D) Tungsten
Ans. (D)

49. For the filament of electric bulb tungsten is used because–
(A) It is a conductor (B) It is cheaper
(C) It is malleable
(D) Its melting point is very high
Ans. (D)

50. What is filled inside an electric bulb?
(A) Nitrogen (B) Carbon dioxide
(C) Argon (D) Oxygen
Ans. (C)

51. A fuse wire can be identify due to the properties–
(A) High Resistivity and minimum melting point
(B) High Resistivity and high melting Point
(C) Minimum Resistivity and minimum melting point
(D) Minimum Resistivity and minimum melting point
Ans. (A)

52. Intensity of magnetic field is–
(A) Meter/volt (B) Meter/ampere
(C) Ampere/meter (D) Volt/ampere
Ans. (C)

53. An electrochemical cell which is used as a
source of direct current at constant voltage
under standard condition is called as–
(A) UPS (uninterrupted power supply)
(B) Battery
(C) Power transmitter
(D) Generator
Ans. (B)

54. The device which is used to store the electric charge is called–
(A) Inductor (B) Capacitor
(C) Generator (D) Transistor
Ans. (B)

55. What is the name of the device which is used to
record the electrical activity during Heart beat?
(A) Electrocardiogram (B) Electrocardiograph
(C) Stethoscope (D) Sphygmomanometer
Ans. (B)

56. Which of the following element is used in a
circuit to block the DC?
(A) Diode (B) Resistor
(C) Inductance (D) Capacitance
Ans. (D)

57. If the length of a resistance wire increases, then its resistance –
(A) Increases (B) Decreases
(C) Remains unchanged
(D) All of these
Ans. (A)

58. If a spoon is to be electroplated with nickel the spoon is.
(A) Dipped in Nickel sulphate solution
(B) Made anode and pure nickel rod, the cathode
(C) Made cathode and pure nickel rod, the anode.
(D) Dry the spoon after plating Nickel sulphate
Ans. (C)

59. If a coil is rotated in a magnetic field, then current is induced in the coi l. This
phenomenon is used in–
(A) For making Electro Magnet
(B) For Making Electric Motor
(C) For Making electric Generator
(D) For making electric watt meter
Ans. (C)

60. When a bar magnet is cut into two equal halves
the pole strength of each piece–
(A) Becomes double (B) Becomes half
(C) Becomes zero (D) Remains the same
Ans. (D)

61. If a Magnet has third pole, then the third pole is called–
(A) Defective pole (B) Consequent pole
(C) Extra pole (D) Arbitrary pole
Ans. (B)

62. Instruments can be shielded from the outside
magnetic effect by surrounding them with–
(A) Iron shield (B) Rubber shield
(C) Brass shield (D) Glass shield
Ans. (B)

63. In electronics what comes under tank circuit?
(A) Resistance and Capacitor
(B) Resistance and Inductance
(C) Capacitor and Inductance
(D) Resistance, Capacitor and Inductance
Ans (C)

64. The substance which conducts current in the solid state is
(A) Diamond (B) Graphite
(C) Iodine (D) Sodium chloride
Ans (B)

65. Good conductor of electricity is
(A) Dry air (B) Paper
(C) Kerosene (D) Graphite
Ans (D)

66. Tungsten is used for the manufacture of the filament of an electric bulb, because
(A) It is a good conductor(B) It is economical
(C) It is malleable
(D) It has a very high melting point
Ans (D)

67. The device which converts AC to DC is
(A) Oscillator (B) Amplifier
(C) Rectifier (D) None of these
Ans (C)

68. When the main switch of the house is put off it disconnects the
(A) Live wire only
(B) Live wire and the earth wire
(C) Live wire and the neutral wire
(D) Earth wire and the neutral wire
Ans (B)

69. Magnetism in materials is due to
(A) Electrons at rest
(B) Circular motion of electrons
(C) Protons at rest
(D) All neutrons at rest
Ans (B)

70. The fuse in our domestic electric circuit melts when there is a high rise in
(A) Inductance (B) Current
(C) Resistance (D) Capacitance
Ans (B)

71. The device used to change the speed of an electric fan is
(A) Amplifier (B) Regulator
(C) Switch (D) Rectifier
Ans (B)

72. A transformer works on the principle of
(A) Self-induction (B) Mutual induction
(C) Generator (D) Inverter
Ans (B)

73. Pure water is bad conductor of electricity because it is
(A) Feebly ionized (B) Not volatile
(C) A very good solvent (D) A non-polar solvent
Ans (D)

74. The nature of fuse wire is
(A) High resistance and low melting point.
(B) High resistance and high melting point.
(C) Low resistance and high melting point.
(D) Low resistance and low melting point.
Ans. (A)

75. Electric current in a metal wire is due to the flow of-
(A) Electrons (B) Protons
(C) Ions (D) Holes
Ans (A)

76. Which of the following is a good conductor of
heat but a bad conductor of electricity?
(A) Celluloid (B) Rubber
(C) Asbestos (D) Mica
Ans. (D)

77. Which of the following is arranged in order of
decreasing conductivity?
(A) Copper, Aluminium, Steel, Silver
(B) Aluminium, Silver, Copper, Steel
(C) Copper, Silver, Aluminium,Steel
(D) Silver, Copper, Aluminium, Steel
Ans. (D)

78. If a copper wire is increased to double its
length, its resistance will become
(A) Four times (B) One-fourth
(C) Double (D) Half
Ans. (C)

79. A device that is used to limit the current in
an electrical circuit is called a
(A) Grid (B) Fuse
(C) Hub (D) Conductor
Ans. (B)

80. The earth-wire of a cable is connected to
(A) The outer metallic body of the appliance
(B) The fuse of the appliance
(C) The filament of the appliance
(D) Short circuit of the appliance
Ans. (B)

81. The metal whose electrical conductivity is more, is
(A) Copper (B) Aluminium
(C) Silver (D) Lead
Ans. (C)

82. Moving electric charge produces:
(A) Magnetic field (B) Sound waves
(C) Light rays (D) Heat waves
Ans. (A)

83. Safety fuse wire used in domestic electrical
appliances is made of metal of low
(A) Resistance (B) Melting point
(C) Specific gravity (D) Conductance
Ans. (B)

84. A fuse wire is made of:
(A) An alloy of tin and copper
(B) An alloy of tin and lead
(C) An alloy of tin and aluminum
(D) An alloy of nickel and chromium
Ans. (B)

85. A transformer works with
(A) Alternating current only
(B) Direct current only
(C) Both AC and DC (D) Any signal
Ans. (A)

86. Which of the following is a good conductor of heat
(A) Mica (B) Asbestos
(C) Celluloid (D) Paraffin wax
Ans. (A)

87. For which of the following substances, the resistance decreases with increases in temperature?
(A) Pure silicon (B) Copper
(C) Nichrome (D) Platinum
Ans. (C)

88. Indicate the false statement about the resistance of a wire
(A) It depends on the material of the wire
(B) It is directly proportional to the length of the wire
(C) It is directly proportional to the area of cross-section of the wire
(D) Resistance of metallic wire increases with increase in temperature
Ans. (C)

89. ‘Farad’ is the unit of:
(A) Capacitance (B) Inductance
(C) Resistance (D) Conductance
Ans. (A)

90. Ohm’s law is valid in case of
(A) Semiconductor (B) Conductor
(C) Superconductor (D) Insulator
Ans. (B)

91. A current carrying conductor is associated with
(A) A magnetic field (B) An electric field
(C) An electro-magnetic field
(D) An electrostatic field
Ans. (A)

92. Super conductors are substances that
(A) Offer minimum resistance to flow of electric current
(B) Conduct electricity at low temperature
(C) Conduct electricity at high temperature
(D) Offer high resistance to the flow of electric current
Ans. (A)

93. In a conductor
(A) There is no conduction band
(B) The forbidden energy gap is very wide
(C) The forbidden energy gap is very narrow
(D) The valence band and the conduction band
overlap each other
Ans. (D)

94. A Fuse wire is characterized by
(A) High resistance and low melting point
(B) High resistance and high melting point
(C) Low resistance and high melting point
(D) Low resistance and low melting point
Ans. (A)

95. Unit of resistance is:
(A) Volt²×ampere (B) Volt/ampere
(C) Ampere/volt (D) Volt × ampere
Ans. (D)

96. S.I. unit of magnetic flux is
(A) Weber (B) Weber/m
(C) Weber/m2 (D) Weber-m²
Ans. (C)

97. To prevent damage from lightning, lightning
conductors are used on tall structures. The
lightning conductor
(A) Should be made of a good conductor but can be of any shape
(B) Should be in the form of a vertical rod
(C) Can be of any shape
(D) Should be made of a good conductor like
copper with sharp-pointed edges
Ans. (D)

98. The magnitude of current flowing between two
end points of a conductor is proportional to
the potential difference between them and is called as:
(A) Avogadro’s law (B) Rault’s law
(C) Ohms law (D) Faraday’s law
Ans. (C)

99. Which of the following was the first theory of super conductivity?
(A) Ginzburg landau theory
(B) London theory
(C) Resonating valence bond theory
(D) Quantum field theory
Ans. (A)

100. A galvanometer can be converted into a
voltmeter by connecting with it a
(A) High resistance in parallel
(B) Low resistance on parallel
(C) High resistance on series
(D) Low resistance in series
Ans. (C)

101. Which one of the following is an ohmic conductor?
(A) Germanium (B) Silicon
(C) Carbon (D) Silver
Ans. (D)

102. Flemings “Left hand Rule” is associated with the effect of
(A) Electric field on current
(B) Magnetic field on magnet
(C) Electric field on magnet
(D) Magnetic Field on current
Ans. (D)

103. An electromagnet is constructed with which of
the following?
(A) Steel (B) Soft Iron
(C) Aluminium (D) Nickel
Ans. (B)

104. Copper wires are generally used for electrical
power transmission instead of iron wire because:
(A) Copper is cheaper than iron
(B) Copper is lighter than iron
(C) Copper is a better conductor of electricity than iron
(D) Copper can take higher power than iron
Ans. (C)

105. The fuse in an electric circuit is connected in
(A) Series with neutral (B) Parallel to live
(C) Parallel to neutral (D) Series with live
Ans. (D)

106. What is the unit of the physical quantity
”Magnetic field stregth”?
(A) Joule per meter (B) Newton per meter
(C) Kelvin per meter (D) Ampere per meter
Ans. (D)

107. Which physical quantity is measured in ‘siemens’?
(A) Electric potential (B) Electrical conductance
(C) Magnetic flux (D) Refractive index
Ans. (B)

108. _____________ states that the total current entering a junction is equal to
the total current leaving the junction.
(A) Lenz’s Law (B) Hooke’s Law
(C) Ohm’s Law (D) Kirchhoff’s First Law
Ans. (D)

109. ___________________states that the induced
e.m.f. is directly proportional to the rate of
change of magnetic flux linkage or rate of
cutting of magnetic flux linkage.
(A) Lenz’s Law (B) Hooke’s Law
(C) Ohm’s Law (D) Faraday’s Law
Ans. (D)

110. What is the unit of the physical quantity “Capacitance”?
(A) Weber (B) Farad
(C) Tesla (D) Ohm
Ans. (B)

111. What is the unit of the physical quantity “Inductance”?
(A) Weber (B) Farad
(C) Henry (D) Tesla
Ans. (C)

112. Unit of impedance is ___________.
(A) Ohm (B) Henry
(C) Tesla (D) Hertz
Ans. (A)

113. Where do the electrical charges reside in a charged conductor?
(A) At the core (B) Throughout the body
(C) Depended upon the nature of the body
(D) On the surface of the body
Ans. (D)

114. If electric resistance is to be decreased, then
the number of resistances should be connected in___
(A) Series (B) Parallel
(C) Mixed arrangement (D) None of these
Ans. (B)

115. The material used in electric heater is
(A) Tungsten (B) Nichrome
(C) Brass (D) Steel
Ans. (B)

116. Which one among the following components is used as an amplifying device?
(A) Transformer (B) Diode
(C) Capacitor (D) Transistor
Ans. (D)

117. The complete form of ‘IC’ in electronics is
(A) Internal circuit (B) Independent circuit
(C) Integrated circuit (D) Inbuilt circuit
Ans. (C)

118. The transformer is a device to convert
(A) D.C. to A.C.
(B) Low voltage D.C. into high voltage D.C.
(C) Low voltage A.C. into high voltage A.C.
(D) Mechanical energy into Electrical energy.
Ans. (C)

119. Which one among the following components
can not be developed within a “integrated circuit”?
(A) Diode (B) Triode
(C) Transformer (D) Transistor
Ans. (C)

120. Maxwell is the unit of which one of the following?
(a) Magnetic flux (b) Permeability
(c) Magnetic susceptibility
(d) Intensity of magnetization
Ans. (A)

121. The force of attraction between an electron
revolving around the nucleus and the nucleus is a ______ force?
(a) Mechanical (b) Electric
(c) Magnetic (d) Gravitational
Ans. (B)

122. Which of the following elements has the highest electrical conductivity?
(a) Copper (b) Silver
(c) Zinc (d) Lead
Ans. (B)

123. What is measured by Ammeter?
(a) Voltage (b) Electric Current
(c) Resistance (d) Conductance
Ans. (B)

124. When resistors are connected in series, then net resistance _____.
(a) Increases (b) Decreases
(c) Remains same (d) None of these
Ans. (A)

125. What is the unit of resistance?
(a) Ohm (b) Farad
(c) Henry (d) Weber
Ans. (A)

126. What is the SI unit of electric current?
(a) Newton (b) Joule
(c) Ampere (d) Watt
Ans. (C)

127. Electric Motor converts _____ energy to mechanical energy
(a) Sound (b) Mechanical
(c) Chemical (d) Electrical
Ans. (D)

128. The force exerted by a magnet is an example of _________.
(a) Non-contact force (b) Muscular force
(c) Contact force (d) Electrostatic force
Ans. (A)

129. The coil wire in the electric room heater or
electric cooking heater is called __________.
(a) Circuit (b) Element
(c) Filament (d) Cells
Ans. (B)

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