Class 12 Physics Ch-7 Alternating Current MCQs Exam 2027

Part 1: Electromagnetic Induction (EMI)

1. The discoverer of the phenomenon of electromagnetic induction was: [BSEB, 2013, 2021]

(A) Faraday

(B) Fleming

(C) Lenz

(D) Rumkorff

2. Lenz’s law is associated with the principle of conservation of: [BSEB, 2015, 2020, 2024]

(A) Charge

(B) Mass

(C) Energy

(D) Momentum

3. The SI unit of Self-Inductance is: [BSEB, 2016, 2022]

(A) Weber (Wb)

(B) Ohm

(C) Henry (H)

(D) Gauss (G)

4. The SI unit of Mutual Induction is: [BSEB, 2024]

(A) Weber

(B) Ohm

(C) Henry

(D) Tesla

5. The SI unit of Magnetic Flux is: [BSEB, 2022]

(A) Tesla (T)

(B) Weber (Wb)

(C) Ampere (A)

(D) Henry (H)

6. The direction of induced electric current is obtained by: [BSEB, 2019]

(A) Fleming’s Left Hand Rule

(B) Lenz’s Law

(C) Maxwell’s Rule

(D) Ampere’s Rule

7. The direction of Eddy Currents can be determined by which law? [BSEB, 2020]

(A) Fleming’s Rule

(B) Lenz’s Law

(C) Maxwell’s Rule

(D) Ampere’s Rule

8. One Henry (1 H) is equal to: [BSEB, 2021]

(A) $10^3$ mH

(B) $10^6$ mH

(C) $10^{-3}$ mH

(D) $10^{-6}$ mH

9. The self-inductance of a coil is a measure of: [BSEB, 2015]

(A) Electrical Inertia

(B) Electrical Friction

(C) Induced E.M.F.

(D) None of these

10. Henry is the unit of: [BSEB, 2018]

(A) Reactance

(B) Inductance

(C) Resistance

(D) None of these

11. The nature of induced electromotive force (e.m.f.) is:

(A) Conservative

(B) Non-conservative

(C) Zero

(D) None of these

12. In electromagnetic induction, the induced charge is independent of: [BSEB, 2015]

(A) Change in flux

(B) Time

(C) Resistance

(D) None of these

13. Magnetic energy stored in an inductor of inductance $L$ carrying current $I$ is: [BSEB, 2021]

(A) $LI^2$

(B) $\frac{1}{2} LI^2$

(C) $\frac{1}{2} L^2 I$

(D) $\frac{1}{2} LI$

14. Who discovered the Dynamo? [BSEB, 2014]

(A) Faraday

(B) Newton

(C) Ampere

(D) Volta

15. The dimensions of inductance are: [BSEB, 2023]

(A) $[ML^2T^{-2}A^{-2}]$

(B) $[ML^2T^{-2}A^{-1}]$

(C) $[MLT^{-2}A^{-2}]$

(D) $[ML^2T^{-1}A^{-2}]$

16. The dimensions of magnetic flux are: [BSEB, 2022]

(A) $[ML^2T^{-2}A^{-1}]$

(B) $[MLT^{-2}A^{-1}]$

(C) $[ML^2T^{-1}A^{-1}]$

(D) $[M^0L^2T^{-2}A^{-1}]$

17. If the magnetic field is uniform but the area of the loop is increased, the flux: [BSEB, 2026]

(A) Increases

(B) Decreases

(C) Becomes zero

(D) Remains unchanged

18. If $\phi$ is the magnetic flux, then the value of induced e.m.f. $e$ is: [BSEB, 2013]

(A) $d\phi / dt$

(B) $-d\phi / dt$

(C) $\phi \cdot t$

(D) $dt / d\phi$

19. The dimensions of induced electromotive force are same as:

(A) Force

(B) Potential Difference

(C) Current

(D) Resistance

20. The unit of self-inductance Weber/Ampere is equal to:

(A) Ohm

(B) Henry

(C) Tesla

(D) Faraday

21. 1 Tesla (T) is equal to:

(A) 1 Weber/meter$^2$

(B) $10^4$ Gauss

(C) Both (A) and (B)

(D) 1 Henry

22. Henry (H), the unit of inductance $L$, is equivalent to:

(A) Volt-second/Ampere

(B) Volt-Ampere/second

(C) Ohm-second

(D) Both (A) and (C)

23. 1 millihenry (1 mH) is equal to:

(A) $10^{-3}$ H

(B) $10^{-6}$ H

(C) $10^3$ H

(D) $10^6$ H

Part 2: Basics of Alternating Current (AC)

24. The mean value of alternating current over a full cycle is: [BSEB, 2024]

(A) Zero

(B) $i/2$

(C) $i$

(D) $2i$

25. The mean value of alternating current over a half cycle is:

(A) Zero

(B) $2I_0 / \pi$

(C) $I_0 / \sqrt{2}$

(D) $\pi I_0 / 2$

26. The ratio of the Root-Mean-Square (RMS) value and the peak value of AC is: [BSEB, 2019, 2026]

(A) $\sqrt{2}$

(B) $1 / \sqrt{2}$

(C) $1 / 2$

(D) $2\sqrt{2}$

27. The peak voltage of an AC supply is 440 V. Its virtual (RMS) voltage is: [BSEB, 2012]

(A) 220 V

(B) 440 V

(C) $220\sqrt{2}$ V

(D) $440\sqrt{2}$ V

28. Alternating current shows which of the following effects?

(A) Chemical

(B) Heating

(C) Magnetic

(D) All of these

29. If the peak value of AC is 10A, its root-mean-square value will be: [BSEB, 2025]

(A) 5 A

(B) 7.07 A

(C) 10 A

(D) 14.14 A

30. In the equation $i = 60 \sin 100 \pi t$, the RMS value of current will be: [BSEB, 2024]

(A) $60 / \sqrt{2}$

(B) 30

(C) 100

(D) Zero

31. The equation of an AC is $i = 50 \sin(100 \pi t)$. Its frequency will be: [BSEB, 2023]

(A) 50 Hz

(B) 100 Hz

(C) 25 Hz

(D) $100 \pi$ Hz

32. Domestic AC voltage is 220 V. What does this represent? [BSEB, 2026]

(A) Peak voltage

(B) Average voltage

(C) Mean voltage

(D) Root-mean-square (RMS) voltage

33. If the frequency of AC is 50 Hz, the rate at which the current becomes zero per second is:

(A) 50 times

(B) 100 times

(C) 200 times

(D) 25 times

34. Virtual current is: [BSEB, 2017]

(A) $\sqrt{2} \times$ Peak current

(B) Peak current / 2

(C) Peak current / $\sqrt{2}$

(D) Average current / $\sqrt{2}$

35. The relation between $I_{rms}$ and Peak value $I_0$ of AC is: [BSEB, 2021]

(A) $I_{rms} = 0.505 I_0$

(B) $I_{rms} = 0.606 I_0$

(C) $I_{rms} = 0.707 I_0$

(D) $I_{rms} = 0.808 I_0$

Part 3: AC Circuits & Impedance

36. The value of Inductive Reactance ($X_L$) is: [BSEB, 2024]

(A) $\omega L$

(B) $\omega / L$

(C) $1 / \omega L$

(D) $\omega^2 L$

37. The value of Capacitive Reactance ($X_C$) is: [BSEB, 2021]

(A) $\omega / c$

(B) $c / \omega$

(C) $\omega \cdot c$

(D) $1 / \omega c$

38. The Inductive Reactance for Direct Current (DC) is: [BSEB, 2022]

(A) Zero

(B) Infinite

(C) $\omega L$

(D) $1 / \omega L$

39. The impedance ($Z$) of an L-R circuit is: [BSEB, 2016, 2020, 2023]

(A) $R + \omega L$

(B) $R^2 + \omega^2 L^2$

(C) $\sqrt{R + \omega L}$

(D) $\sqrt{R^2 + \omega^2 L^2}$

40. The impedance ($Z$) of an L-C-R circuit is: [BSEB, 2020, 2023]

(A) $\sqrt{R^2 + (\omega L – 1/\omega C)^2}$

(B) $R + \omega L + 1/\omega C$

(C) $\sqrt{R^2 + \omega^2 L^2}$

(D) $R^2 + (\omega L – 1/\omega C)^2$

41. The unit of impedance is: [BSEB, 2024]

(A) Henry

(B) Ohm

(C) Tesla

(D) None of these

42. In a purely capacitive AC circuit, the phase difference between current and voltage is: [BSEB, 2023, 2025, 2026]

(A) 0°

(B) 90°

(C) 180°

(D) 45°

43. In a capacitive AC circuit, current _______ the potential difference: [BSEB, 2026]

(A) Leads (Forward)

(B) Lags (Backward)

(C) Is in the same phase

(D) None of these

44. The dimensional formula for $L/R$ and $RC$ is: [BSEB, 2021]

(A) $[M^0L^0T^{-1}], [M^0L^0T^{-1}]$

(B) $[M^0L^0T], [M^0L^0T]$

(C) $[M^0L^0T], [M^0L^0T^{-1}]$

(D) $[M^0L^0T^0], [M^0L^0T^0]$

45. A capacitor is an ideal insulator for: [BSEB, 2026]

(A) AC

(B) DC

(C) Both AC and DC

(D) None of these

46. For electrical resonance in an L-C-R circuit, it is necessary that: [BSEB, 2020]

(A) $\omega L = 1 / \omega C$

(B) $\omega L = \omega C$

(C) $\omega = \omega C$

(D) None of these

47. The frequency of an L-C circuit is:

(A) $f = 1 / \sqrt{LC}$

(B) $f = 1 / (2\pi \sqrt{LC})$

(C) $f = (1 / 2\pi) \sqrt{L/C}$

(D) $f = 2\pi \sqrt{C/L}$

48. In an (L-R) circuit, the phase difference ($\phi$) is: [BSEB, 2022]

(A) $\sin^{-1} ( \omega L / R )$

(B) $\cos^{-1} ( \omega L / R )$

(C) $\tan^{-1} ( \omega L / R )$

(D) $\tan^{-1} ( R / \omega L )$

49. For Direct Current (DC), the reactance of a capacitor ($X_C$) is: [BSEB, 2021]

(A) Zero

(B) Finite

(C) Infinite

(D) $\omega C$

50. In an AC circuit $R = 8 \Omega$ and $X_L = 6 \Omega$ are connected in series. The impedance will be: [BSEB, 2013]

(A) $2 \Omega$

(B) $10 \Omega$

(C) $14 \Omega$

(D) $48 \Omega$

51. $\frac{1}{2\pi \sqrt{LC}}$ is equal to the unit of:

(A) Frequency

(B) Time

(C) Velocity

(D) Acceleration

52. In a purely resistive circuit, the phase difference between voltage and current is:

(A) $0^\circ$

(B) $90^\circ$

(C) $180^\circ$

(D) $45^\circ$

53. In L-C oscillations, the exchange of energy occurs between:

(A) Only Electric field

(B) Only Magnetic field

(C) Between Electric and Magnetic fields

(D) None of these

54. The dimensional formula for Reactance ($X$) is:

(A) $[ML^2T^{-3}A^{-2}]$

(B) $[ML^2T^{-2}A^{-2}]$

(C) $[MLT^{-3}A^{-2}]$

(D) $[ML^2T^{-3}A^{-1}]$

55. The formula for Q-factor (Quality factor) is:

(A) $\frac{1}{R} \sqrt{\frac{L}{C}}$

(B) $R \sqrt{\frac{L}{C}}$

(C) $\frac{1}{R} \sqrt{\frac{C}{L}}$

(D) $LCR$

56. For maximum current in an L-C-R circuit:

(A) $\omega^2 = LC$

(B) $\omega^2 = 1 / LC$

(C) $\omega = 1 / LC$

(D) $\omega = \sqrt{LC}$

57. If the phase difference in an L-R circuit is $\phi$, then $\tan \phi$ will be: [BSEB, 2019]

(A) $\omega L / R$

(B) $R / \omega L$

(C) $\omega L \cdot R$

(D) $\omega / LR$

58. In an AC circuit with angular frequency $\omega$, the inductive reactance produced by inductor $L$ is: [BSEB, 2021]

(A) $\omega / L$

(B) $\omega \cdot L$

(C) $1 / (\omega \cdot L)$

(D) $L \cdot \omega$

59. The unit of $1 / L\omega$ is: [BSEB, 2017]

(A) Same as $R$

(B) Same as $L\omega$

(C) Both

(D) None of these

60. The dimensions of $L/R$ are same as which of the following? [BSEB, 2023]

(A) $RC$

(B) $\sqrt{RC}$

(C) $1 / RC$

(D) $(RC)^2$

Part 4: Power & Power Factor

61. Which of the following relations is correct for Power Factor? [BSEB, 2021, 2025]

(A) Power Factor = True Mean Power $\times$ Apparent Mean Power

(B) Power Factor = Apparent Mean Power / True Mean Power

(C) Power Factor = True Mean Power / Apparent Mean Power

(D) Power Factor = 1/2 [True Mean Power $\times$ Apparent Mean Power]

62. In a purely inductive circuit, the value of Power Factor is: [BSEB, 2025]

(A) 0

(B) 1

(C) 0.5

(D) Infinite

63. The expression for True Mean Power in an AC circuit is: [BSEB, 2022]

(A) $P_{av} = E_{rms} \cos \phi$

(B) $P_{av} = I_{rms} \cos \phi$

(C) $P_{av} = E_{rms} I_{rms} \sin \phi$

(D) $P_{av} = E_{rms} I_{rms} \cos \phi$

64. If phase difference between $I$ and $V$ is $\phi$, the wattless component of current is: [BSEB, 2019]

(A) $I \cos \phi$

(B) $I \tan \phi$

(C) $I \sin \phi$

(D) $I \cos^2 \phi$

65. The Power Factor of an L-R circuit is: [BSEB, 2019]

(A) $R^2 + \omega L$

(B) $\omega L / R$

(C) $R / \sqrt{R^2 + (\omega L)^2}$

(D) $R \cdot \sqrt{R^2 + \omega^2 L^2}$

66. If $i = i_0 \sin \omega t$ and $V = V_0 \sin (\omega t + \pi/2)$, the power dissipated will be: [BSEB, 2018]

(A) $V_0 i_0$

(B) $V_0 i_0 / 2$

(C) $V_0 i_0 / \sqrt{2}$

(D) Zero

67. In an AC circuit, power is only consumed in: [BSEB, 2024]

(A) Resistance

(B) Inductance

(C) Capacitance

(D) All of these

68. If the phase difference is $\phi$, then the value of Power Factor is: [BSEB, 2015, 2024]

(A) $\tan \phi$

(B) $\sin \phi$

(C) $\cos^2 \phi$

(D) $\cos \phi$

69. The Power Factor of Wattless Current is: [BSEB, 2024]

(A) 0

(B) 1

(C) 0.5

(D) Infinite

70. If $i = 5 \cos \omega t$ A and $V = 200 \sin \omega t$ V, the power loss in the circuit is: [BSEB, 2018]

(A) 20 W

(B) 40 W

(C) 1000 W

(D) Zero

71. In resonance condition in an L-C-R circuit, the phase difference is: [BSEB, 2023]

(A) $\pi$

(B) $\pi / 2$

(C) $\pi / 4$

(D) Zero

72. In a circuit at resonance, the Power Factor is:

(A) Zero

(B) $0.5$

(C) $1$

(D) Infinite

73. The maximum value of Power Factor in an AC circuit is: [BSEB, 2020]

(A) 0

(B) 1

(C) 0.5

(D) Infinite

74. The Power Factor of a capacitor is approximately:

(A) 90

(B) 1

(C) 180

(D) 0

75. The power of an electric circuit is: [BSEB, 2016, 2021]

(A) $V \cdot R$

(B) $V^2 \cdot R$

(C) $V^2 / R$

(D) $V^2 \cdot R \cdot I$

76. The property of a circuit that converts electrical energy into heat is:

(A) Inductance

(B) Resistance

(C) Capacitance

(D) E.M.F.

Part 5: Devices – Transformer, Dynamo, and Meters

77. A Transformer is a device for: [BSEB, 2021]

(A) Converting AC to DC

(B) Converting DC to AC

(C) Increasing or decreasing DC voltage

(D) Increasing or decreasing AC voltage

78. Which of the following is not possible in a Transformer? [BSEB, 2021]

(A) Eddy Currents

(B) Direct Current (DC)

(C) Alternating Current (AC)

(D) Induced Current

79. In a Step-up Transformer, $N_1$ and $N_2$ are number of turns in primary and secondary coils: [BSEB, 2017]

(A) $N_1 > N_2$

(B) $N_2 > N_1$

(C) $N_1 = N_2$

(D) $N_1 = 0$

80. Which quantity decreases in a Step-down Transformer? [BSEB, 2020, 2026]

(A) Current

(B) Voltage

(C) Frequency

(D) Power

81. The most suitable material for making the core of a Transformer is: [BSEB, 2023]

(A) Soft Iron

(B) Steel

(C) Copper

(D) Aluminum

82. A Hot Wire Ammeter measures which value of AC? [BSEB, 2016, 2020, 2024]

(A) Peak value

(B) Average value

(C) Root-Mean-Square value

(D) None of these

83. A device that converts mechanical energy into electrical energy is called: [BSEB, 2019]

(A) Transformer

(B) Dynamo

(C) Motor

(D) Induction Coil

84. The transformation ratio in a Transformer is: [BSEB, 2022]

(A) $V_s / V_p$

(B) $V_p / V_s$

(C) $I_s / I_p$

(D) $1 / (I_s I_p)$

85. Choke Coil works on the principle of: [BSEB, 2016, 2026]

(A) Self-induction

(B) Mutual induction

(C) Wattless current

(D) Eddy current

86. In a Step-up Transformer, the value of current in the secondary coil compared to the primary is: [BSEB, 2023, 2025]

(A) Equal

(B) Less

(C) More

(D) None of these

87. The core of a Transformer is laminated to:

(A) Increase current

(B) Get high potential

(C) Reduce loss due to Eddy Currents

(D) Gain more energy

88. The working principle of a Dynamo is based on: [BSEB, 2015, 2021]

(A) Heating effect of current

(B) Electromagnetic Induction

(C) Induced Magnetism

(D) Induced Electricity

89. Hot Wire Ammeter and Hot Wire Voltmeter are based on which effect of current? [BSEB, 2024]

(A) Magnetic

(B) Chemical

(C) Heating

(D) Electromagnetic

90. To convert a Galvanometer into a Voltmeter, we need: [BSEB, 2017, 2022]

(A) High Resistance

(B) Low Resistance

(C) Capacitor

(D) Induction coil

91. Which of the following devices is based on Electromagnetic Induction? [BSEB, 2025]

(A) Voltmeter

(B) Electric Motor

(C) Electric Generator

(D) Ammeter

92. From a Step-up Transformer, we get:

(A) High voltage and low current

(B) Low voltage and high current

(C) Low voltage and low current

(D) High voltage and high current

93. The conversion of electrical energy into heat in a transformer is called: [BSEB, 2018]

(A) Copper Loss

(B) Iron Loss

(C) Hysteresis Loss

(D) None of these

94. The AC voltage across a resistor can be measured by:

(A) Potentiometer

(B) Hot Wire Voltmeter

(C) Moving Coil Galvanometer

(D) Moving Magnet Galvanometer

95. In a Step-up Transformer, if potential difference in primary and secondary are $V_1$ and $V_2$: [BSEB, 2018]

(A) $V_1 > V_2$

(B) $V_2 > V_1$

(C) $V_1 = V_2$

(D) $V_1 = 0$

96. Which quantity remains unchanged in a Transformer? [BSEB, 2022]

(A) Voltage

(B) Current

(C) Frequency

(D) None of these

97. An example of Mutual Induction is:

(A) Dynamo

(B) Transformer

(C) Choke Coil

(D) Ammeter

98. The efficiency of an ideal Transformer is:

(A) 50%

(B) 90%

(C) 100%

(D) 25%

99. Iron Loss can be reduced by using:

(A) Copper wire

(B) Soft iron core

(C) Laminated core

(D) None of these

100. A Transformer works on the principle of: [BSEB, 2015, 2021]

(A) Self-induction

(B) Mutual Induction

(C) Eddy currents

(D) Magnetic induction

101. Copper Loss in a transformer occurs in which part?

(A) Core

(B) Windings

(C) Oil

(D) None of these

102. The current used in Electroplating is: [BSEB, 2024]

(A) DC

(B) AC

(C) Both

(D) None of these

Part 6: Additional Important Practice Questions (103-135)

103. An ammeter of $0.05 \Omega$ resistance is connected to a 1.5 V cell. If 2.0 A current flows, the internal resistance of the cell is: [BSEB, 2010]

(A) $1.0 \Omega$

(B) $0.9 \Omega$

(C) $0.8 \Omega$

(D) $0.7 \Omega$

104. In the equation $i = 60 \sin 100 \pi t$, the frequency is: [BSEB, 2015, 2024]

(A) 50 Hz

(B) 100 Hz

(C) $50\pi$ Hz

(D) 60 Hz

105. The unit of Inductive Reactance is: [BSEB, 2016, 2018]

(A) Ohm

(B) Mho

(C) Farad

(D) Ampere

106. The Power Factor of a Choke Coil is approximately: [BSEB, 2025]

(A) 0

(B) 1

(C) 0.5

(D) 100

107. Ampere-hour is a unit of:

(A) Power

(B) Charge

(C) Energy

(D) Potential Difference

108. In an L-C-R series circuit, current is maximum if: [BSEB, 2010]

(A) $\omega < 1 / \sqrt{LC}$

(B) $\omega = 1 / \sqrt{LC}$

(C) $\omega > 1 / \sqrt{LC}$

(D) $\omega = LC$

109. Alternating current is measured by:

(A) Moving Coil Galvanometer

(B) Hot Wire Ammeter

(C) Voltmeter

(D) DC Ammeter

110. The dimension $[ML^2T^{-2}A^{-1}]$ of flux $\phi$ is same as:

(A) Potential

(B) Work

(C) Energy

(D) None of these

111. When a magnet is brought towards a coil, the induced e.m.f. depends on:

(A) Speed of magnet

(B) Number of turns

(C) Magnetic strength

(D) All of the above

112. Wattless Current is used in:

(A) Choke coil

(B) Heater

(C) Bulb

(D) None of these

113. Impedance ($Z$) of an L-C-R circuit at resonance is:

(A) Zero

(B) Equal to $R$

(C) Infinite

(D) $(\omega L + 1/\omega C)$

114. A Capacitor blocks DC because:

(A) Its reactance is infinite

(B) It is an insulator

(C) Both (A) and (B)

(D) None of these

115. DC is more dangerous than AC because:

(A) Its value remains constant

(B) It has electrolytic effect

(C) Peak value is high

(D) This statement is wrong

116. Self-inductance and Mutual induction both have unit Henry. 1 Henry is equal to:

(A) $10^9$ emu

(B) $1$ Wb/A

(C) Both (A) and (B)

(D) $1$ V/A

117. Turns in primary are 500 and in secondary are 5000. The transformer is:

(A) Step-down

(B) Step-up

(C) Constant potential

(D) None of these

118. In an L-C-R circuit, the value of Power Factor $\cos \phi$ is:

(A) $R/Z$

(B) $Z/R$

(C) $R \cdot Z$

(D) $1/RZ$

119. Why is average AC over a full cycle zero?

(A) Because it changes direction

(B) Because peak value is constant

(C) Net flow of charge is zero

(D) Both (A) and (C)

120. Dimensional formula of $RC$ is: [BSEB, 2022]

(A) $M^0 L^0 T^{-1}$

(B) $M^0 L^0 T$

(C) $M^0 L^0 T^0$

(D) $M L T^2$

121. Which is correct for a Step-up Transformer? [BSEB, 2022]

(A) $V_s < V_p$

(B) $V_s > V_p$

(C) $V_s \ll V_p$

(D) $V_s = V_p$

122. The working principle of Choke Coil is based on: [BSEB, 2016]

(A) Conservation of angular momentum

(B) Self-induction

(C) Mutual induction

(D) Conservation of momentum

123. In a purely capacitive AC circuit, the phase difference is: [BSEB, 2023]

(A) 0°

(B) 90°

(C) 180°

(D) 45°

124. In the equation $i = 60 \sin 100 \pi t$, the RMS value and Frequency are: [BSEB, 2017]

(A) $60/\sqrt{2}$ A, 50 Hz

(B) $30\sqrt{2}$ A, 50 Hz

(C) 30 A, 50 Hz

(D) $60\sqrt{2}$ A, 100 Hz

125. Hot wire ammeter measures which value of AC? [BSEB, 2024]

(A) Peak

(B) Average

(C) Root-mean-square

(D) None of these

126. Inductive Reactance ($X_L$) is: [BSEB, 2024]

(A) $\omega L$

(B) $\omega / L$

(C) $1 / \omega L$

(D) $\omega^2 L$

127. Who discovered Electromagnetic Induction? [BSEB, 2021]

(A) Faraday

(B) Fleming

(C) Lenz

(D) Rumkorff

128. The unit of Inductance $L$ is:

(A) Weber/Ampere

(B) Volt-second/Ampere

(C) Henry

(D) All of the above

129. Resonant circuits are used in:

(A) Radio tuning

(B) Voltage regulation

(C) Increasing current

(D) None of these

130. Dimension of $L/R$ is equal to:

(A) Frequency

(B) Time period

(C) Velocity

(D) Acceleration

131. When $X_L = X_C$ in an L-C-R circuit, the circuit is:

(A) Inductive

(B) Capacitive

(C) Resistive

(D) None of these

132. Impedance $Z$ is measured in Ohms ($\Omega$). It represents:

(A) Total obstruction to AC

(B) Only Resistance

(C) Only Reactance

(D) E.M.F.

133. Average power loss in a purely capacitive circuit is:

(A) $P = VI$

(B) $P = 0$

(C) $P = I^2 R$

(D) $P = V/I$

134. Eddy Currents are used in:

(A) Induction furnace

(B) Speedometer

(C) Magnetic brakes in trains

(D) All of the above

135. 1 Henry is equal to:

(A) $10^3$ millihenry

(B) $10^6$ microhenry

(C) Both (A) and (B)

(D) $10^{-3}$ Henry