This quiz works best with JavaScript enabled. Home > Class 12 > Class 12 Physics (Part I) Chapter 7 Alternating Current – Quiz 2 🏠 Homepage 📘 Download PDF Books 📕 Premium PDF Books Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 2 (25 MCQs) Quiz Instructions Select an option to see the correct answer instantly. 1. The root mean square current ( $I_{rms}$ A) Peak. B) Least. C) Average. D) Effective. Show Answer Correct Answer: D) Effective. 2. Mean value of ac for half cycle is A) Zero. B) $\frac{i_0}{\sqrt{2}}$. C) $\frac{2i_0}{\pi}$. D) None. Show Answer Correct Answer: C) $\frac{2i_0}{\pi}$. 3. Unit of voltage is A) Ampere. B) MA. C) Volt. D) Watt. Show Answer Correct Answer: C) Volt. 4. UCLES N78/II/22; CIE J84/II/24. In an ideal transformer, the most important function of the soft-iron core is A) To reduce eddy currents. B) To improve the flux-linkage between the primary and secondary coils. C) To dissipate the heat generated by the two coils. D) To produce a uniform radial field in the two coils. Show Answer Correct Answer: B) To improve the flux-linkage between the primary and secondary coils. 5. AC frequency in Pakistan mains supply is: A) 60 Hz. B) 100 Hz. C) 50 Hz. D) 25 Hz. Show Answer Correct Answer: C) 50 Hz. 6. What is one of the main advantages of using alternating current (a.c.)? A) It produces less arcing and sparking on contacts. B) It is more efficient than d.c. C) It requires less maintenance. D) It is more environmentally friendly. Show Answer Correct Answer: A) It produces less arcing and sparking on contacts. 7. Select the correct phrase: A) In a capacitive circuit the voltage leads the current. B) In an inductive circuit the current lags the voltage. C) In a resistive circuit, the current and voltage are out of phase. D) In a capacitive circuit the current lags the voltage. Show Answer Correct Answer: B) In an inductive circuit the current lags the voltage. 8. Which of the following best describes the waveform of a single-phase AC? A) Square wave. B) Sine wave. C) Triangle wave. D) Sawtooth wave. Show Answer Correct Answer: B) Sine wave. 9. AC is converted from one level of voltage for transmission and then reduced to a different level of voltage for utilization by the end-user by using? . A) Inverters. B) Rectifiers. C) Transformers. D) Generators. Show Answer Correct Answer: C) Transformers. 10. In LCR circuit if resistance increases, quality factor A) Increases finitely. B) Decreases finitely. C) Remains constant. D) None of these. Show Answer Correct Answer: B) Decreases finitely. 11. Out of the following, choose the correct relation A) 1H= 1V/1A. B) 1H= 1A/1V. C) 1H= 1V/1A/s. D) 1H= 1V/1As. Show Answer Correct Answer: C) 1H= 1V/1A/s. 12. An alternating voltage has the equation V(t) = (150 sin 3881t) V, determine instantaneous voltage when t = 5 ms. A) 67.3 V. B) 75.5 V. C) 79.1 V. D) 80.9 V. Show Answer Correct Answer: C) 79.1 V. 13. Consider an RLC circuit that is driven by an AC applied voltage. At resonance, A) The peak voltage across the capacitor is greater than the peak voltage across the inductor. B) The peak voltage across the inductor is greater than the peak voltage across the capacitor. C) The current is in phase with the driving voltage. D) The peak voltage across the resistor is equal to the peak voltage across the inductor. Show Answer Correct Answer: C) The current is in phase with the driving voltage. 14. A resistor is connected to an AC power supply. On this circuit, the current A) Leads the voltage by 90$^\circ$. B) Lags the voltage by 90$^\circ$. C) Is in same phase with the voltage. D) None of the given answers. Show Answer Correct Answer: C) Is in same phase with the voltage. 15. What is the effect of inductance in an AC circuit? A) Increases resistance. B) Stores energy in a magnetic field. C) Decreases voltage. D) Stores energy as heat. Show Answer Correct Answer: B) Stores energy in a magnetic field. 16. What is the definition of alternating current (AC)? A) Alternating current (AC) is a current that never changes direction. B) Alternating current (AC) is a type of static electricity. C) Alternating current (AC) is an electric current that periodically reverses direction. D) Direct current (DC) flows in one direction only. Show Answer Correct Answer: C) Alternating current (AC) is an electric current that periodically reverses direction. 17. In an ideal 1:8 step-down transformer, the primary power is 10 kW and the secondary current is 25 A. The primary voltage is: A) 25, 600 V. B) 3200 V. C) 400 V. D) 50 V. Show Answer Correct Answer: B) 3200 V. 18. Describe the role of inductance in an AC circuit. A) Inductance has no effect on AC circuits and only applies to DC circuits. B) Inductance increases current flow without any phase shift. C) Inductance reduces the overall resistance in a circuit without affecting reactance. D) Inductance opposes changes in current, creates a phase shift, and contributes to reactance in AC circuits. Show Answer Correct Answer: D) Inductance opposes changes in current, creates a phase shift, and contributes to reactance in AC circuits. 19. How does the frequency affect the reactance of an inductor? A) The reactance of an inductor decreases with frequency. B) The reactance of an inductor remains constant regardless of frequency. C) The reactance of an inductor increases with frequency. D) The reactance of an inductor is independent of the frequency applied. Show Answer Correct Answer: C) The reactance of an inductor increases with frequency. 20. What is the significance of the root mean square (RMS) value in AC circuits? A) The RMS value is irrelevant in AC circuits. B) The RMS value represents the average power delivered by an AC circuit. C) The RMS value is the peak value of the AC signal. D) The RMS value is only applicable to DC circuits. Show Answer Correct Answer: B) The RMS value represents the average power delivered by an AC circuit. 21. How do transformers work in AC circuits? A) Transformers convert DC to AC power directly. B) Transformers use mechanical gears to transfer energy. C) Transformers only work with resistive loads. D) Transformers work by using electromagnetic induction to transfer energy between coils in an AC circuit. Show Answer Correct Answer: D) Transformers work by using electromagnetic induction to transfer energy between coils in an AC circuit. 22. Which of the following is true about capacitors in ac circuit? A) Voltage across capacitor leads current. B) The current decreases when frequency decreases. C) Instantaneous power is zero. D) Mean power is zero. Show Answer Correct Answer: D) Mean power is zero. 23. Explain the significance of RMS values in AC circuits. A) RMS values are significant in AC circuits as they represent the effective voltage or current, allowing for accurate power calculations and comparisons with DC systems. B) RMS values are only relevant for DC circuits. C) RMS values indicate the peak voltage in AC circuits. D) RMS values are used to measure resistance in circuits. Show Answer Correct Answer: A) RMS values are significant in AC circuits as they represent the effective voltage or current, allowing for accurate power calculations and comparisons with DC systems. 24. In a region of uniform magnetic induction $B=10^{-2}$ $\pi^2$ A) $4\\pi^2$. B) 30 mA. C) 6 mA. D) 200 mA. Show Answer Correct Answer: C) 6 mA. 25. What role does phase difference play in resonance circuits? A) At resonance, phase difference is always 90 degrees. B) Phase difference indicates the relationship between voltage and current; at resonance, it is zero, maximizing power transfer. C) Phase difference only affects the frequency of the circuit. D) Phase difference is irrelevant in resonance circuits. Show Answer Correct Answer: B) Phase difference indicates the relationship between voltage and current; at resonance, it is zero, maximizing power transfer. ← PreviousNext →Related QuizzesClass 12 Physics (Part I) Chapter 7 Alternating Current Quiz 1Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 3Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 4Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 5Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 6Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 7Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 8Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 9Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 10Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 11 🏠 Back to Homepage 📘 Download PDF Books 📕 Premium PDF Books