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Chapter 7: Alternating Current

NCERT Solutions for CBSE Class 10 Physics — 105 solved questions with detailed explanations.

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Solved Questions

Q1. In a pure capacitive AC circuit, the current:

Lags voltage by 90°
Leads voltage by 90°
Is in phase with voltage
Leads voltage by 45°

Difficulty: Easy · Topic: AC Circuits

Solution

In capacitive circuit, I leads V by 90° (or π/2). I = C dV/dt.

Q2. A transformer works on the principle of:

Self induction
Mutual induction
Electrostatic induction
Electromagnetic radiation

Difficulty: Easy · Topic: Transformer

Solution

Transformers work on mutual induction: changing current in primary induces EMF in secondary.

Q3. At resonance in a series LCR circuit:

Impedance is maximum
Current is maximum
Voltage across L = Voltage across R
Power factor is zero

Difficulty: Easy-Medium · Topic: Resonance

Solution

At resonance X_L = X_C, impedance Z = R (minimum), current is maximum, power factor = 1.

Q4. In a pure inductive circuit, current:

lags by 45°
is in phase
leads voltage by 90°
lags voltage by 90°

Difficulty: Easy-Medium · Topic: AC Concepts

Solution

lags voltage by 90°.

Q5. Power factor of a pure resistive circuit is:

0.5
infinity
0
1

Difficulty: Easy-Medium · Topic: AC Concepts

Solution

1.

Q6. Power factor of a purely reactive circuit is:

infinity
0
1
0.5

Difficulty: Easy-Medium · Topic: AC Concepts

Solution

0.

Q7. Wattless current flows in:

purely resistive circuit
series LCR at resonance
all circuits
purely reactive circuit

Difficulty: Easy-Medium · Topic: AC Concepts

Solution

purely reactive circuit.

Q8. RMS value of AC is:

peak/√2
peak×√2
peak/2
peak

Difficulty: Easy-Medium · Topic: AC Concepts

Solution

peak/√2.

Q9. The quality factor Q of a series LCR resonant circuit is:

ωL/R
R/ωL
1/ωCR
Both A and C

Difficulty: Medium · Topic: Q Factor

Solution

Q = ω₀L/R = 1/(ω₀CR) = (1/R)√(L/C). Both A and C are correct expressions.

Q10. In a series LCR circuit with R=30Ω, X_L=50Ω, X_C=10Ω, the impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(X_L-X_C)²) = √(30²+(50-10)²) = 50.0 Ω.

Q11. In a series LCR circuit with R=40Ω, X_L=60Ω, X_C=20Ω, the impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(X_L-X_C)²) = √(40²+(60-20)²) = 56.57 Ω.

Q12. In a series LCR circuit with R=50Ω, X_L=50Ω, X_C=50Ω, the impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(X_L-X_C)²) = √(50²+(50-50)²) = 50.0 Ω.

Q13. In a series LCR circuit with R=100Ω, X_L=150Ω, X_C=50Ω, the impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(X_L-X_C)²) = √(100²+(150-50)²) = 141.42 Ω.

Q14. In a series LCR circuit with R=20Ω, X_L=40Ω, X_C=10Ω, the impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(X_L-X_C)²) = √(20²+(40-10)²) = 36.06 Ω.

Q15. In series LCR (R=20Ω, X_L=40Ω, X_C=10Ω), impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(XL-XC)²).

Q16. In series LCR (R=30Ω, X_L=45Ω, X_C=15Ω), impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(XL-XC)²).

Q17. In series LCR (R=40Ω, X_L=50Ω, X_C=20Ω), impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(XL-XC)²).

Q18. In series LCR (R=50Ω, X_L=55Ω, X_C=25Ω), impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(XL-XC)²).

Q19. In series LCR (R=60Ω, X_L=60Ω, X_C=30Ω), impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(XL-XC)²).

Q20. In series LCR (R=70Ω, X_L=65Ω, X_C=35Ω), impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(XL-XC)²).

Q21. In series LCR (R=80Ω, X_L=70Ω, X_C=40Ω), impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(XL-XC)²).

Q22. In series LCR (R=90Ω, X_L=75Ω, X_C=45Ω), impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(XL-XC)²).

Q23. In series LCR (R=100Ω, X_L=80Ω, X_C=50Ω), impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(XL-XC)²).

Q24. In series LCR (R=110Ω, X_L=85Ω, X_C=55Ω), impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(XL-XC)²).

Q25. In series LCR (R=120Ω, X_L=90Ω, X_C=60Ω), impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(XL-XC)²).

Q26. In series LCR (R=130Ω, X_L=95Ω, X_C=65Ω), impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(XL-XC)²).

Q27. In series LCR (R=140Ω, X_L=100Ω, X_C=70Ω), impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(XL-XC)²).

Q28. In series LCR (R=150Ω, X_L=105Ω, X_C=75Ω), impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(XL-XC)²).

Q29. In series LCR (R=160Ω, X_L=110Ω, X_C=80Ω), impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(XL-XC)²).

Q30. In series LCR (R=170Ω, X_L=115Ω, X_C=85Ω), impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(XL-XC)²).

Q31. In series LCR (R=180Ω, X_L=120Ω, X_C=90Ω), impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(XL-XC)²).

Q32. In series LCR (R=190Ω, X_L=125Ω, X_C=95Ω), impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(XL-XC)²).

Q33. In series LCR (R=200Ω, X_L=130Ω, X_C=100Ω), impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(XL-XC)²).

Q34. In series LCR (R=210Ω, X_L=135Ω, X_C=105Ω), impedance is:

Difficulty: Medium · Topic: Impedance

Solution

Z = √(R²+(XL-XC)²).

Q35. LCR: R=10Ω, XL=10Ω, XC=0Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=14.14 Ω.

Q36. LCR: R=10Ω, XL=10Ω, XC=10Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=10.0 Ω.

Q37. LCR: R=10Ω, XL=10Ω, XC=20Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=14.14 Ω.

Q38. LCR: R=10Ω, XL=10Ω, XC=30Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=22.36 Ω.

Q39. LCR: R=10Ω, XL=10Ω, XC=40Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=31.62 Ω.

Q40. LCR: R=10Ω, XL=10Ω, XC=50Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=41.23 Ω.

Q41. LCR: R=10Ω, XL=10Ω, XC=60Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=50.99 Ω.

Q42. LCR: R=10Ω, XL=10Ω, XC=70Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=60.83 Ω.

Q43. LCR: R=10Ω, XL=10Ω, XC=80Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=70.71 Ω.

Q44. LCR: R=10Ω, XL=10Ω, XC=90Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=80.62 Ω.

Q45. LCR: R=10Ω, XL=20Ω, XC=0Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=22.36 Ω.

Q46. LCR: R=10Ω, XL=20Ω, XC=10Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=14.14 Ω.

Q47. LCR: R=10Ω, XL=20Ω, XC=20Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=10.0 Ω.

Q48. LCR: R=10Ω, XL=20Ω, XC=30Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=14.14 Ω.

Q49. LCR: R=10Ω, XL=20Ω, XC=40Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=22.36 Ω.

Q50. LCR: R=10Ω, XL=20Ω, XC=50Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=31.62 Ω.

Q51. LCR: R=10Ω, XL=20Ω, XC=60Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=41.23 Ω.

Q52. LCR: R=10Ω, XL=20Ω, XC=70Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=50.99 Ω.

Q53. LCR: R=10Ω, XL=20Ω, XC=80Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=60.83 Ω.

Q54. LCR: R=10Ω, XL=20Ω, XC=90Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=70.71 Ω.

Q55. LCR: R=10Ω, XL=30Ω, XC=0Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=31.62 Ω.

Q56. LCR: R=10Ω, XL=30Ω, XC=10Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=22.36 Ω.

Q57. LCR: R=10Ω, XL=30Ω, XC=20Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=14.14 Ω.

Q58. LCR: R=10Ω, XL=30Ω, XC=30Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=10.0 Ω.

Q59. LCR: R=10Ω, XL=30Ω, XC=40Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=14.14 Ω.

Q60. LCR: R=10Ω, XL=30Ω, XC=50Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=22.36 Ω.

Q61. LCR: R=10Ω, XL=30Ω, XC=60Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=31.62 Ω.

Q62. LCR: R=10Ω, XL=30Ω, XC=70Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=41.23 Ω.

Q63. LCR: R=10Ω, XL=30Ω, XC=80Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=50.99 Ω.

Q64. LCR: R=10Ω, XL=30Ω, XC=90Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=60.83 Ω.

Q65. LCR: R=10Ω, XL=40Ω, XC=0Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=41.23 Ω.

Q66. LCR: R=10Ω, XL=40Ω, XC=10Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=31.62 Ω.

Q67. LCR: R=10Ω, XL=40Ω, XC=20Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=22.36 Ω.

Q68. LCR: R=10Ω, XL=40Ω, XC=30Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=14.14 Ω.

Q69. LCR: R=10Ω, XL=40Ω, XC=40Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=10.0 Ω.

Q70. LCR: R=10Ω, XL=40Ω, XC=50Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=14.14 Ω.

Q71. LCR: R=10Ω, XL=40Ω, XC=60Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=22.36 Ω.

Q72. LCR: R=10Ω, XL=40Ω, XC=70Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=31.62 Ω.

Q73. LCR: R=10Ω, XL=40Ω, XC=80Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=41.23 Ω.

Q74. LCR: R=10Ω, XL=40Ω, XC=90Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=50.99 Ω.

Q75. LCR: R=10Ω, XL=50Ω, XC=0Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=50.99 Ω.

Q76. LCR: R=10Ω, XL=50Ω, XC=10Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=41.23 Ω.

Q77. LCR: R=10Ω, XL=50Ω, XC=20Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=31.62 Ω.

Q78. LCR: R=10Ω, XL=50Ω, XC=30Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=22.36 Ω.

Q79. LCR: R=10Ω, XL=50Ω, XC=40Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=14.14 Ω.

Q80. LCR: R=10Ω, XL=50Ω, XC=50Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=10.0 Ω.

Q81. LCR: R=10Ω, XL=50Ω, XC=60Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=14.14 Ω.

Q82. LCR: R=10Ω, XL=50Ω, XC=70Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=22.36 Ω.

Q83. LCR: R=10Ω, XL=50Ω, XC=80Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=31.62 Ω.

Q84. LCR: R=10Ω, XL=50Ω, XC=90Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=41.23 Ω.

Q85. LCR: R=10Ω, XL=60Ω, XC=0Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=60.83 Ω.

Q86. LCR: R=10Ω, XL=60Ω, XC=10Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=50.99 Ω.

Q87. LCR: R=10Ω, XL=60Ω, XC=20Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=41.23 Ω.

Q88. LCR: R=10Ω, XL=60Ω, XC=30Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=31.62 Ω.

Q89. LCR: R=10Ω, XL=60Ω, XC=40Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=22.36 Ω.

Q90. LCR: R=10Ω, XL=60Ω, XC=50Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=14.14 Ω.

Q91. LCR: R=10Ω, XL=60Ω, XC=60Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=10.0 Ω.

Q92. LCR: R=10Ω, XL=60Ω, XC=70Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=14.14 Ω.

Q93. LCR: R=10Ω, XL=60Ω, XC=80Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=22.36 Ω.

Q94. LCR: R=10Ω, XL=60Ω, XC=90Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=31.62 Ω.

Q95. LCR: R=10Ω, XL=70Ω, XC=0Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=70.71 Ω.

Q96. LCR: R=10Ω, XL=70Ω, XC=10Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=60.83 Ω.

Q97. LCR: R=10Ω, XL=70Ω, XC=20Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=50.99 Ω.

Q98. LCR: R=10Ω, XL=70Ω, XC=30Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=41.23 Ω.

Q99. LCR: R=10Ω, XL=70Ω, XC=40Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=31.62 Ω.

Q100. LCR: R=10Ω, XL=70Ω, XC=50Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=22.36 Ω.

Q101. LCR: R=10Ω, XL=70Ω, XC=60Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=14.14 Ω.

Q102. LCR: R=10Ω, XL=70Ω, XC=70Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=10.0 Ω.

Q103. LCR: R=10Ω, XL=70Ω, XC=80Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=14.14 Ω.

Q104. LCR: R=10Ω, XL=70Ω, XC=90Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=22.36 Ω.

Q105. LCR: R=10Ω, XL=80Ω, XC=0Ω. Z:

Difficulty: Medium · Topic: Impedance

Solution

Z=√(R²+(XL-XC)²)=80.62 Ω.

Other Chapters in Physics

Ch 1: Electric Charges & Fields Ch 2: Electrostatic Potential Ch 3: Current Electricity Ch 4: Moving Charges & Magnetism Ch 5: Magnetism & Matter Ch 6: Electromagnetic Induction Ch 8: Electromagnetic Waves Ch 9: Ray Optics Ch 10: Wave Optics Ch 11: Dual Nature of Radiation Ch 12: Atoms Ch 13: Nuclei Ch 14: Semiconductor Electronics

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