1. Instrument which cconverts mechanical energy to electrical energy is:
(A) Induction-coil
(B) Dynamo
(C) Transformer
(D) Motor
Multiple Choice
ID- 15796
BSEB, 2020 (A)
2. Which quantity decrease in step-down transformer?
(A) Current
(B) Voltage
(C) Power
(D) Frequency
Multiple Choice
ID- 15797
BSEB, 2013; 2016 (A), 2017 (A)
3. The unit of reactance is:
(A) mho
(B) ohm
(C) farad
(D) ampere
Multiple Choice
ID- 15798
BSEB, 2010
4. An a.c. source of angular frequency ω is connected in a series LCR circuit. The peak value of current will be maximum when:
(A) ω < $\frac{1}{\sqrt{LC}}$
(B) ω < $\sqrt{LC}$
(C) ω = $\frac{1}{\sqrt{LC}}$
(D) ω > $\frac{1}{\sqrt{LC}}$
Multiple Choice
ID- 15799
BSEB, 2010
5. A cell of e.m.f. 1.5 V is connected with an ammeter of resistance of 0.05 Ω. If the current in the circuit is 2.0 A, the internal resistance of the cell is:
(A) 1.0 Ω
(B) 0.9 Ω
(C) 0.8 Ω
(D) 0.7 Ω
Multiple Choice
ID- 15800
BSEB, 2012
6. The peak voltage of an a.c. is 440 volt. Its virtual voltage is:
(A) 220 V
(B) 440 V
(C) 220 $\sqrt{2}$ V
(D) 440 $\sqrt{2}$ V
Multiple Choice
ID- 15801
BSEB, 2015
7. If ф is the phase difference between a.c. current and e.m.f., then the value of power factor is:
(A) tan ф
(B) $\ce{cos^2}$ ф
(C) sin ф
(D) cos ф
Multiple Choice
ID- 15802
BSEB, 2015, 2018 (C), 2020 (A)
8. Impedance of L-R circuit is:
(A) $\ce{R^2 + ωL^2}$
(B) $\ce{\sqrt{R + ωL}}$
(C) $\ce{R + ωL}$
(D) $\ce{\sqrt{R^2 + ω^2L^2}}$
Multiple Choice
ID- 15803
9. Direction of current induced in a wire moving in a magnetic field is found using:
(A) Fleming's left hand rule
(B) Fleming's right hand rule
(C) Ampere's rule
(D) Right hand claps rule
Multiple Choice
ID- 15804
BSEB, 2016
10. Lenz's law is a consequence of the law of conservation of:
(A) charge
(B) energy
(C) induced emf
(D) induced current
Multiple Choice
ID- 15805
11. Which of the following does not of application of eddy current?
(A) Electric power meters
(B) Induction fornace
(C) LED lights
(D) Magnetic brakes in trains
Multiple Choice
ID- 15806
12. Induction furnace make use of:
(A) self induction
(B) mutual induction
(C) eddy current
(D) none of these
Multiple Choice
ID- 15807
BSEB, 2021 (A)
13. One Henry is equal to:
(A) $\ce{10^3 mH}$
(B) $\ce{10^6 mH}$
(C) $\ce{10^{–3} mH}$
(D) $\ce{10^{–6} mH}$
Multiple Choice
ID- 15808
BSEB, 2021 (A)
14. The relation between r.m.s. value of alternating current $\ce{I_{r.m.s.}) }$ and peak value of alternating current $\ce{(I_0)}$ is:
(A) $\ce{I_{r.m.s.} = 0.505 I_0}$
(B) $\ce{I_{r.m.s.} = 0.606 I_0}$
(C) $\ce{I_{r.m.s.} = 0.707 I_0}$
(D) $\ce{I_{r.m.s.} = 0.808 I_0}$
Multiple Choice
ID- 15809
15. If N is the number of turns in a coil, the value of self-inductance varies as:
(A) $\ce{N^0}$
(B) $\ce{N}$
(C) $\ce{N^2}$
(D) $\ce{N^{–2}}$
Multiple Choice
ID- 15810
16. Two solenoids of equal number of turns have their lengths and the radii in the same ratio 1 : 2. The ratio of their self inductances will be:
(A) 1 : 2
(B) 2 : 1
(C) 1 : 1
(D) 1 : 4
Multiple Choice
ID- 15811
17. If the number of turns per unit length of a coil of solenoid is doubled, the self-inductance of the solenoid will:
(A) remain unchanged
(B) be halved
(C) be doubled
(D) become four times
Multiple Choice
ID- 15812
18. If coefficient of mutual industance of two coils depends on:
(A) medium between the coils
(B) distance between the two coils
(C) orientation of the two coils
(D) all of these
Multiple Choice
ID- 15813
19. A solenoid is connected to a battery so that a steady current flows through it. If an iron core is instead into the solenoid the current will:
(A) increase
(B) decrease
(C) remain same
(D) first increase then decrease
Multiple Choice
ID- 15814
20. The physical quantity which is measured in the unit of $\ce{Wb A^{–1}}$ is:
(A) self inductance
(B) mutual inductance
(C) megnetic flux
(D) both 'A' and 'B'
Multiple Choice
ID- 15815
21. The phase difference ф is related to path difference ∆x by:
(A) $\ce{\frac{λ}{π}}$ ф
(B) $\ce{\frac{π}{λ}}$ ф
(C) $\ce{\frac{λ}{2π}}$ ф
(D) $\ce{\frac{2π}{λ}}$ ф
Multiple Choice
ID- 15816
22. A 100 mH coil carries a current of 1 A. Energy stored in its magnetic field is:
(A) 0.5 J
(B) 0.05 J
(C) 1 J
(D) 0.1 J
Multiple Choice
ID- 15817
23. The unit of inductance is equivalent to:
(A) $\ce{\frac{volt x ampere}{second}}$
(B) $\ce{\frac{ampere}{volt x second}}$
(C) $\ce{\frac{volt}{ampere x second}}$
(D) $\ce{\frac{volt x second}{ampere}}$
Multiple Choice
ID- 15818
24. If the self inductance of 500 turns coil is 125 mH, then the self inductance of the similar soil of 800 turns is:
(A) 48.8 mH
(B) 200 mH
(C) 290 mH
(D) 320 mH
Multiple Choice
ID- 15819
25. Two identical coaxial coils P and Q carrying equal amount of current in the same direction are bought nearer. The current in:
(A) P increases while in Q decreses
(B) Q increases with in P decreases
(C) both P and Q increases
(D) both P and Q increases
Multiple Choice
ID- 15820
26. When a wire loop is rotated in a magnetic field, the direction of induced emf changes in every:
(A) one revolution
(B) $\frac{1}{2}$ revolution
(C) $\frac{1}{4}$ revolution
(D) 2 revolution
Multiple Choice
ID- 15821
27. The energy stored in an inductor of self inductance L henry carrying a current of I ampere is:
(A) $\ce{\frac{1}{2}L^2I}$
(B) $\ce{\frac{1}{2}LI^2}$
(C) $\ce{LI^2}$
(D) $\ce{L^2I}$
Multiple Choice
ID- 15822
28. Faraday's laws are consequence of the conservation of:
(A) charge
(B) energy
(C) magnetic field
(D) both 'B' and 'C'
Multiple Choice
ID- 15823
29. 1 henry is equal to:
(A) $\ce{\frac{weber}{ampere}}$
(B) $\ce{\frac{weber}{volt}}$
(C) weber ampere
(D) None of these
Multiple Choice
ID- 15824
BSEB, 2018 (C)
30. Henry is unit of:
(A) Inductance
(B) Magnetic flux
(C) Magnetic field
(D) Electric field
Multiple Choice
ID- 15825
BSEB, 2018 (C), 2019 (A)
31. The working of a dynamo is based on the principal of:
(A) Heating effect of electric current
(B) Electromagnetic Induction
(C) Chemical effect of electric current
(D) None of the above
Multiple Choice
ID- 15826
32. A transformer is used to light 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 A. Then the efficiency of the transformer is:
(A) 11%
(B) 50%
(C) 80%
(D) 90%
Multiple Choice
ID- 15827
33. The magnetic flux (ф) linked with a coil is related to it's area (s) as:
(A) ф $\ce{\propto s}$
(B) ф $\ce{\propto s^2}$
(C) ф $\ce{\propto 5^{1/2}}$
(D) ф $\ce{\propto s^{–1/2}}$
Multiple Choice
ID- 15828
34. The magnetic flux (ф) lined with a coil is related to the number of turns (N) of the coil as:
(A) ф $\ce{\propto N}$
(B) ф $\ce{\propto N^{–1}}$
(C) ф $\ce{\propto N^2}$
(D) ф $\ce{\propto N^{–2}}$
Multiple Choice
ID- 15829
35. The role of inductance is equivalent to:
(A) interia
(B) force
(C) energy
(D) momentum
Multiple Choice
ID- 15830
36. A coil of L = 8.4 mH and R = 6Ω is connected to a 12 V battery. The current in the coil is 1.0 A at approx time of:
(A) 500 s
(B) 20 s
(C) 35 ms
(D) 1 ms
Multiple Choice
ID- 15831
37. The average value of actually over a complete cycle is:
(A) $\ce{I_0}$
(B) $\ce{I^0}$
(C) $\ce{\frac{I_0}{\sqrt{2}}}$
(D) zero
Multiple Choice
ID- 15832
38. A disc of radius 0.1 m is rotating with a frequency 10 rev/sec. in a normal magnetic field of strength 0.1 tesla. Net induced emf is:
(A) $\ce{2π x 10^{–2} V}$
(B) $\ce{4π x 10^{–4} V}$
(C) $\ce{π x 10^{–2} V}$
(D) $\ce{3π x 10^{–2} V}$
Multiple Choice
ID- 15833
39. A wire of length 50 cm moves with a velocity of 300 m/min, perpendicular to a magnetic field. If the emf induced in the wire is 2V, the magnitude of the filed in tesla is:
(A) 2
(B) 5
(C) 0.4
(D) 0.8
Multiple Choice
ID- 15834
40. Who discovered that electric field is produced in a conductor when magnetic lines force intercepting it change?
(A) Maxwell
(B) Oerstred
(C) Lenz
(D) Faraday
Multiple Choice
ID- 15835
41. Power factor of an accident circuit is a measure of:
(A) virtual power
(B) power lost in the circuit
(C) mean power
(D) all the above
Multiple Choice
ID- 15836
42. The dimensional formula of L/R is similar to that of:
(A) frequency
(B) time
(C) length
(D) none of these
Multiple Choice
ID- 15837
43. The dimensional formula of impedance is:
(A) $\ce{[ML^2T^{–2}A^{–2}]}$
(B) $\ce{[ML^2T^{–3}A^{–2}]}$
(C) $\ce{[ML^2T^{–2}A^{–1}]}$
(D) $\ce{[ML^2T^{–2}A^{–3}]}$
Multiple Choice
ID- 15838
44. An iron core transformer with a turns ratio 8 : 1 has 120 V applied across the primary. The voltage across the secondary equals.
(A) 15 V
(B) 120 V
(C) 180 V
(D) 960 V
Multiple Choice
ID- 15839
45. A choke is used as a resistance in:
(A) dc circuits
(B) ac circuits
(C) both ac and dc circuits
(D) neither (A) nor (B)
Multiple Choice
ID- 15840
46. The SI unit of magnetic flux is:
(A) $\ce{T}$
(B) $\ce{Tm^{–2}}$
(C) $\ce{Wb}$
(D) $\ce{Wb m^{–2}}$
Multiple Choice
ID- 15841
47. For purely capacitive circuits, power factor is:
(A) 0
(B) –1
(C) 1
(D) infinity
Multiple Choice
ID- 15842
48. The magnetic flux linked with a coil is inversely proportional to the
(A) magnetic field
(B) area of cross section
(C) number of turns
(D) none of the above
Multiple Choice
ID- 15843
49. The energy stored in a 50 mH inductor carrying a current of 4A is:
(A) 0.1 J
(B) 0.4 J
(C) 0.04 J
(D) 0.01 J
Multiple Choice
ID- 15844
50. The core of a transformer is laminated because:
(A) rusting of core may be prevented
(B) ratio of voltage in primary and secondary may be increased.
(C) energy losses due to eddy current may be minimised
(D) The weight of transformer may be reduced
Multiple Choice
ID- 15845
BSEB, 2021 (A)
51. Inductive reactance offered by an inductor of inductance L in ac circuit of angular frequency ω is:
(A) $\ce{\frac{ω}{L}}$
(B) $\ce{ω · L}$
(C) $\ce{\frac{1}{ω · L}}$
(D) $\ce{\frac{L}{ω}}$
Multiple Choice
ID- 15846
BSEB, 2016
52. The dimensional formula of induced emf is:
(A) $\ce{[ML^2T^{–2}A^{–1}]}$
(B) $\ce{[ML^2T^{–3}A^{–1}]}$
(C) $\ce{[ML^2T^{–3}A^{–2}]}$
(D) $\ce{[ML^2T^{–2}A^{–2}]}$
Multiple Choice
ID- 15847
53. The dimensional formula of the coefficient of self inductance is:
(A) $\ce{[ML^2T^{–2}]}$
(B) $\ce{[ML^2T^{–2}A^{–1}]}$
(C) $\ce{[ML^2T^{–2}A^{–2}]}$
(D) $\ce{[ML^2T^{–3}A^{–2}]}$
Multiple Choice
ID- 15848
BSEB, 2019 (A)
54. The ratio of root mean square (rms) value and peak value of an alternating current is:
(A) $\sqrt{2}$
(B) $\frac{1}{\sqrt{2}}$
(C) $\frac{1}{2}$
(D) 2$\sqrt{2}$
Multiple Choice
ID- 15849
BSEB, 2019 (A), 2019 (C)
55. In a step-up transformer, no. of turns in primary and secondary coils are $\ce{N_1}$ and $\ce{N_2}$ then:
(A) $\ce{N_1 > N_2}$
(B) $\ce{N_2 > N_1}$
(C) $\ce{N_1 = N_2}$
(D) $\ce{N_1 = 0}$
Multiple Choice
ID- 15850
BSEB, 2018 (C)
56. In an alternating current circuit, the pase difference between current I and voltage in ф, the Wattless component of current will be:
(A) I cos ф
(B) I tan ф
(C) I sin ф
(D) I $\ce{cos^2}$ ф
Multiple Choice
ID- 15851
57. Transformer works on the principal of:
(A) Convertor
(B) invertor
(C) mutual induction
(D) self-induction
Multiple Choice
ID- 15852
58. Which of the following effects is not shown in alternating current?
(A) Chemical effect
(B) Magnetic effect
(C) Heating current
(D) All of these
Multiple Choice
ID- 15853
59. An ac ammeter connected in series in an circuit reads 5A. The peak value of current:
(A) 5A
(B) 5 $\sqrt{2}$ A
(C) $\frac{5}{\sqrt{5}}$ A
(D) zero
Multiple Choice
ID- 15854
60. Which of the following relationship is correct for power factor?
(A) Power factor = True average power x Apparent average power
(B) Power factor = $\ce{\frac{Apparent average power}{True average power}}$
(C) Power factor = $\ce{\frac{True average power}{Apparent average power}}$
(D) Power factor = $\frac{1}{2}$ [True average power x Apparent average power]
Multiple Choice
ID- 15855
61. Faraday constant:
(A) depends on the amount of the electrolyte
(B) depends on the current in the electrolyte
(C) is a universal constant
(D) depends on the amount of charge passed through the electrolyte
Multiple Choice
ID- 15856
62. A reject cicuit is:
(A) series resonant circuit
(B) paralle resonant circuit
(C) LCR circuit
(D) None of these
Multiple Choice
ID- 15857
63. The inductive reactance of an inductor coil of $\frac{1}{π}$ H at 50 Hz is:
(A) $\frac{50}{π}$ Ω
(B) $\frac{π}{50}$ Ω
(C) 100 Ω
(D) 50 Ω
Multiple Choice
ID- 15858
BSEB, 2021 (A)
64. Capacitive reactance is:
(A) $\frac{w}{π}$
(B) $\frac{c}{w}$
(C) w · c
(D) $\frac{1}{wc}$
Multiple Choice
ID- 15859
BSEB, 2021 (A)
65. Which of the following is correct for transformer?
(A) It converts A.C. into D.C.
(B) It converts D.C. into A.C.
(C) It increases or decreses D.C. voltage
(D) It increases or decreses A.C. voltage
Multiple Choice
ID- 15860
66. Two coils X and Y ate connected in series across a 240 V, 50 Hz supply. The resistance of X is 5Ω and inductance of Y is 0.02 H. The power consumed in 3 kW and the power factor is 0.75. The impedance of the circuit is:
(A) 0.144 Ω
(B) 1.44 Ω
(C) 14.4 Ω
(D) 144 Ω
Multiple Choice
ID- 15861
67. A chock coil is a coil having:
(A) low inductance and high resistance
(B) low inductance and low resistance
(C) high inductance and high resistance
(D) high inductance and negligence resistance
Multiple Choice
ID- 15862
68. Quantity that remains unchanged in a transformer is:
(A) frequency
(B) current
(C) voltage
(D) None of these
Multiple Choice
ID- 15863
69. Which quantity in increased in a step-down transformer?
(A) Current
(B) Voltage
(C) Power
(D) Frequency
Multiple Choice
ID- 15864
70. Skin effect is associated with:
(A) a.c. only
(B) d.c only
(C) a.c. and d.c. both
(D) None of these
Multiple Choice
ID- 15865
71. Power factor in series LCR circuit is:
(A) R/Z
(B) R.Z
(C) Z/R
(D) ωL/R
Multiple Choice
ID- 15866
72. In L-C-R circuit produce resonance:
(A) ωc = $\frac{1}{ωL}$
(B) ωL = $\frac{1}{ωc}$
(C) ωL = ωc
(D) None
Multiple Choice
ID- 15867
73. In A.C. circuit:
(A) frequency does not depend upon impedance
(B) frequency increases with impedance
(C) frquency decreases with impedance
(D) frequency in universely proportional to impedance
Multiple Choice
ID- 15868
74. The peak voltage of 220 V A.C. mains is:
(A) 155.6
(B) 220
(C) 311
(D) 440
Multiple Choice
ID- 15869
75. The voltage and current in an A.C. are given by V = 5 sin (100 $π$t – $π$/6); I = (100 $π$t + $π$/6), then:
(A) voltage leads current by 30°
(B) current leads voltage by 60°
(C) current leads voltage by 30°
(D) voltage leads current by 60°
Multiple Choice
ID- 15870
BSEB, 2016
76. Hot wire ammeter measures:
(A) peak value of ac
(B) average value of ac
(C) r.m.s. ac
(D) none of these
Multiple Choice
ID- 15871
BSEB, 2016
77. If $\ce{N_1}$ and $\ce{N_2}$ are numbers of primary and secondary coils of a step-up transformer, then:
(A) $\ce{N_1}$ > $\ce{N_2}$
(B) $\ce{N_2}$ > $\ce{N_1}$
(C) $\ce{N_1}$ = $\ce{N_2}$
(D) $\ce{N_1}$ = 0
Multiple Choice
ID- 15872
BSEB, 2016, 2019 (A)
78. The power factor of L-R circuit is:
(A) R + WL
(B) $\ce{\frac{R}{\sqrt{R^2 + W^2L^2}}}$
(C) $\ce{R\sqrt{R^2 + W^2L^2}}$
(D) WL/R
Multiple Choice
ID- 15873
BSEB, 2016
79. When an ammeter is shuted, its measuring range
(A) increases
(B) decreases
(C) remains constant
(D) none of these
Multiple Choice
ID- 15874
BSEB, 2017 (A)
80. The relation between peak current $\ce{I_0}$ and root mean square current $\ce{I_{rms}}$ is:
(A) $\ce{I_0 = \sqrt{2}I_{rms}}$
(B) $\ce{I_0 = I_{rms}}$
(C) $\ce{I_0 = 2I_{rms}}$
(D) $\ce{I_0 = \frac{I_{rms}}{\sqrt{2}}}$
Multiple Choice
ID- 15875
BSEB, 2018 (A)
81. A charge 'q' moves in a region where electric field 'E' and magnetic field 'B' both exist, then force on it is:
(A) $\ce{q}$ ($\overset{→}{v}$ x $\overset{→}{B}$)
(B) $\ce{q \overset{→}{E}}$
(C) $\ce{q}$ {$\overset{→}{E}$ + ($\overset{→}{v}$ x $\overset{→}{B}$)}
(D) $\ce{q}$ {$\overset{→}{B}$ + ($\overset{→}{v}$ x $\overset{→}{B}$)}
Multiple Choice
ID- 15876
BSEB, 2018 (A)
82. A circular coil of radius r carries a current I. The magnetic field at its centre is B. At what distance from the centre, or the axis of the coil, the magnetic field will be B/8:
(A) $\sqrt{2}$R
(B) 2R
(C) $\sqrt{3}$R
(D) 3R
Multiple Choice
ID- 15877
BSEB, 2017 (C)
83. Unit of $\ce{\frac{1}{Lw}}$ is unit of:
(A) R
(B) Lw
(C) Both 'A' and 'B'
(D) None of these
Multiple Choice
ID- 15878
BSEB, 2017 (C)
84. The convert a galvanometer into voltmeter requirement is of:
(A) high resistance
(B) low resistance
(C) condenser
(D) inductor
Multiple Choice
ID- 15879
BSEB, 2017 (C)
85. S.I. unit of decay constant is:
(A) hertz
(B) meter
(C) per meter
(D) none of these
Multiple Choice
ID- 15880
BSEB, 2018 (A)
86. In A.C. circuits, the current and voltage are given by I = 5 cos wt, and V = 200 sin wt respectively. Power loss in the circuit is:
(A) 20 W
(B) 40 W
(C) 1000 W
(D) zero
Multiple Choice
ID- 15881
BSEB, 2018 (A)
87. The value of maximum amplitude produced due to interference of two waves is given by y = 4 sin wt and $y_2$ = 3 cos wt.
(A) 7
(B) 5
(C) 1
(D) 25
Multiple Choice
ID- 15882
BSEB, 2017 (C)
88. If phase difference between current and potential difference is φ, then power factor will be: