Alternating Current MCQs for Board Exams
Alternating Current – MCQs for Board Exams
Class: 12 | Subject: Physics |
Section: Electromagnetic Induction & Alternating Current |
Topic: Alternating Current
Based on: NCERT Syllabus | CBSE Board Examination Standard
Based on: NCERT Syllabus | CBSE Board Examination Standard
Instructions: These Multiple Choice Questions (MCQs) are designed strictly as per the NCERT syllabus, making them ideal for CBSE Class 12 Board Examination preparation.
1. Alternating current changes:
Answer: C
AC varies sinusoidally with time.
AC varies sinusoidally with time.
2. SI unit of frequency:
Answer: B
Measured in Hz.
Measured in Hz.
3. Time period T =
Answer: B
T = 1/f.
T = 1/f.
4. RMS value of AC is:
Answer: B
Equivalent DC heating effect.
Equivalent DC heating effect.
5. RMS current Irms =
Answer: B
Standard RMS relation.
Standard RMS relation.
6. Peak factor =
Answer: A
I₀/Irms.
I₀/Irms.
7. AC generator works on:
Answer: A
Electromagnetic induction.
Electromagnetic induction.
8. Power factor =
Answer: B
Phase angle cosine.
Phase angle cosine.
9. Pure resistor phase difference:
Answer: A
Voltage & current in phase.
Voltage & current in phase.
10. Pure inductor phase difference:
Answer: B
Current lags voltage.
Current lags voltage.
11. Pure capacitor phase difference:
Answer: B
Current leads voltage.
Current leads voltage.
12. Inductive reactance XL =
Answer: A
Opposition by inductor.
Opposition by inductor.
13. Capacitive reactance XC =
Answer: A
Opposition by capacitor.
Opposition by capacitor.
14. Impedance unit:
Answer: B
Same as resistance.
Same as resistance.
15. Resonance occurs when:
Answer: A
Net reactance zero.
Net reactance zero.
16. Power consumed in pure L or C:
Answer: B
No real power loss.
No real power loss.
17. AC mains frequency in India:
Answer: B
Standard supply frequency.
Standard supply frequency.
18. Step‑up transformer increases:
Answer: B
Voltage increases.
Voltage increases.
19. Efficiency of ideal transformer:
Answer: C
No losses assumed.
No losses assumed.
20. Average power in AC circuit:
Answer: B
Includes power factor.
Includes power factor.
