This quiz works best with JavaScript enabled. Home > Cbse > Class 12 > Science > Physics Part I > Class 12 Physics (Part I) Chapter 7 Alternating Current – Quiz 16 🏠 Homepage 📘 Download PDF Books 📕 Premium PDF Books Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 16 (58 MCQs) Quiz Instructions Select an option to see the correct answer instantly. 1. What is meant by the peak voltage in an alternating voltage? A) The minimum voltage reached. B) The average voltage over a cycle. C) The voltage at zero crossing. D) The maximum voltage reached. Show Answer Correct Answer: D) The maximum voltage reached. 2. What is the purpose of using a step-up transformer in power stations? A) To increase voltage for long-distance transmission. B) To convert a.c. to d.c. C) To decrease voltage for local distribution. D) To stabilise voltage fluctuations. Show Answer Correct Answer: A) To increase voltage for long-distance transmission. 3. Which of the following statement is TRUE concerning the impedance of an RCL circuit? A) The impedance is dominated by C at high frequencies. B) The impedance is dominated by L at high frequencies. C) The impedance depends only on the value R. D) The impedance depends only on the value C and L only. Show Answer Correct Answer: B) The impedance is dominated by L at high frequencies. 4. The value of inductive reactance is A) 62.8 $\Omega$. B) 0.1 $\Omega$. C) 14 $\Omega$. D) 31.4. Show Answer Correct Answer: D) 31.4. 5. The root mean square of the alternating current is equal to A) $\frac{1}{\sqrt[]{2}}$. B) Half the peak value. C) Equal to peak value. D) Twice the peak value. Show Answer Correct Answer: A) $\frac{1}{\sqrt[]{2}}$. 6. Which of the following statements CORRECTLY shows the effect on X$_{L}$ when f is increased to 2f? A) X$_{L}$ decreases by a factor of two. B) X$_{L}$ increases by a factor of two. C) X$_{L}$ decreases by a factor of four. D) X$_{L}$ increases by a factor of four. Show Answer Correct Answer: B) X$_{L}$ increases by a factor of two. 7. What is not the reason for the loss of power in the transformer A) Heat loss due to the resistance of the coils. B) Leakage of magnetic field lines between the primary and secondary coils. C) Heat loss due to eddy currents induced in the iron core. D) Heat loss due to radiation of electromagnetic waves. E) Heat loss due to repeated magnetization and demagnetization of the core. Show Answer Correct Answer: D) Heat loss due to radiation of electromagnetic waves. 8. What is the term for a current that reverses its direction periodically? A) Alternating Current (AC). B) Pulsating Current. C) Direct Current (DC). D) Static Current. Show Answer Correct Answer: A) Alternating Current (AC). 9. Phase angle is the ..... A) Total phase between current and voltage in DC circuit. B) Phase difference between current and voltage in DC circuit. C) Total phase between current and voltage in AC circuit. D) Phase difference between current and voltage in AC circuit. Show Answer Correct Answer: D) Phase difference between current and voltage in AC circuit. 10. The opposition to current flow offered by an inductor in an AC circuit is A) Inductance. B) Capacitive Reactance. C) Inductive Reactance. D) None of the above. Show Answer Correct Answer: C) Inductive Reactance. 11. What happens to the current in an R.L.C circuit at resonance? A) The current fluctuates wildly. B) The current is zero. C) The current reaches its maximum value. D) The current is halved. Show Answer Correct Answer: C) The current reaches its maximum value. 12. Fill in the blank:The overall length of course of treatment is usually longer than the ..... A) Dose. B) Session. C) Blend. D) Interval. Show Answer Correct Answer: C) Blend. 13. What does the term 'smoothing' refer to in the context of rectification? A) Decreasing the frequency of the output. B) Reducing the current through the load. C) Making the voltage output more stable. D) Increasing the peak voltage. Show Answer Correct Answer: C) Making the voltage output more stable. 14. What words are missing from the following statement? The impedance of a series RCL circuit at resonance will be ..... and equal to the circuit ..... A) Minimum and resistance. B) Maximum and resistance. C) Minimum and reactance. D) Maximum and reactance. Show Answer Correct Answer: A) Minimum and resistance. 15. In an LCR circuit capacitance is changed from C to 2 C. For the resonant frequency to remain unchanged, the inductance should be changed from L to A) L/4. B) L/2. C) 4/L. D) 2 L. Show Answer Correct Answer: B) L/2. 16. An AC source produces emf E=E$^\circ$ sin wt. The rms value depends directly on: A) Frequency only. B) Angular frequency only. C) Time period only. D) Peak value only. Show Answer Correct Answer: D) Peak value only. 17. What does electromotive force (emf) represent? A) A type of electrical resistance. B) An electrical action produced by a non-electrical source. C) The strength of a magnetic field. D) The speed of a conductor. Show Answer Correct Answer: B) An electrical action produced by a non-electrical source. 18. ..... is a representation of how alternating current varies with time. A) WAVEFORM. B) VOLTAGE. C) CURRENT. D) None of the above. Show Answer Correct Answer: A) WAVEFORM. 19. Current from a battery is A) DC. B) BC. C) AC/DC. D) AC. Show Answer Correct Answer: A) DC. 20. If the frequency of A.C is large, the reactance of capacitor is A) Large. B) Small. C) Zero. D) None. Show Answer Correct Answer: B) Small. 21. How does the phase angle in an AC circuit affect power consumption? A) Power consumption is solely dependent on voltage and not affected by phase angle. B) The phase angle affects power consumption by determining the relationship between voltage and current, influencing real power usage. C) A larger phase angle always increases power consumption. D) The phase angle has no impact on power consumption. Show Answer Correct Answer: B) The phase angle affects power consumption by determining the relationship between voltage and current, influencing real power usage. 22. The combined effect of resistance and reactance in AC circuit is called A) Capacitance. B) Inductance. C) Impedance. D) Conductance. Show Answer Correct Answer: C) Impedance. 23. How does phase difference affect the performance of AC motors? A) Phase difference only affects DC motors, not AC motors. B) Phase difference affects AC motor performance by influencing torque, efficiency, and potential overheating. C) Phase difference improves the lifespan of AC motors. D) Phase difference has no impact on AC motor performance. Show Answer Correct Answer: B) Phase difference affects AC motor performance by influencing torque, efficiency, and potential overheating. 24. In a purely resistive AC circuit, the instantaneous power is: A) Maximum at current zero. B) Sometimes positive, sometimes negative. C) Always positive. D) Always zero. Show Answer Correct Answer: C) Always positive. 25. In an ac circuit, peak value of voltage is 423 volts. Its effective voltage is ..... A) 340 volts. B) 300 volts. C) 400 volts. D) 323 volts. Show Answer Correct Answer: B) 300 volts. 26. How does the power factor affect the efficiency of an AC circuit? A) A high power factor always increases circuit voltage. B) A low power factor guarantees higher current flow. C) The power factor affects efficiency by determining how much of the supplied power is used for useful work; a low power factor reduces efficiency. D) Power factor has no impact on circuit performance. Show Answer Correct Answer: C) The power factor affects efficiency by determining how much of the supplied power is used for useful work; a low power factor reduces efficiency. 27. What is a choke coil used for in AC circuits? A) Block higher-frequency AC. B) Decrease voltage. C) Increase frequency. D) Increase current. Show Answer Correct Answer: A) Block higher-frequency AC. 28. What device changes the voltage of an AC supply using electromagnetic induction? A) Capacitor. B) Transformer. C) Generator. D) Rectifier. Show Answer Correct Answer: B) Transformer. 29. The value of a given waveform at any instant time is termed as ..... A) Instantaneous value. B) Waveform. C) Cycle. D) Period. Show Answer Correct Answer: A) Instantaneous value. 30. Induced emf in a conductor of length l rotated with angular velocity w in a uniform magnetic field B is A) E = 2Bl$^{2}$w. B) E = Bl$^{2}$w. C) E = Bl$^{2}$w/2. D) E = Blw. Show Answer Correct Answer: C) E = Bl$^{2}$w/2. 31. How does a three-phase system benefit over a single-phase system? A) It requires less wiring. B) It provides a constant power delivery. C) It is cheaper to install. D) It is used only for small appliances. Show Answer Correct Answer: B) It provides a constant power delivery. 32. What is phasor diagram? A) A vector that rotates anticlockwise about its axis with constant angular acceleration. B) A vector that rotates clockwise about its axis with constant angular velocity. C) A vector that rotates clockwise about its axis with constant angular acceleration. D) A vector that rotates anticlockwise about its axis with constant angular velocity. Show Answer Correct Answer: D) A vector that rotates anticlockwise about its axis with constant angular velocity. 33. Same current is flowing in two alternating circuits. The first circuit contains only inductance and the other contains only a capacitor. If the frequency of the emf of AC is increased, the effect on the value of the current A) Increases in the first circuit and decreases in the other. B) Increases in both the circuits. C) Decreases in both the circuits. D) Decreases in the first circuit and increases in the other. Show Answer Correct Answer: D) Decreases in the first circuit and increases in the other. 34. Why is power factor correction important in electrical systems? A) To reduce energy losses, improve voltage stability, increase system capacity, and lower electricity costs. B) To maintain the power factor at an inefficient level. C) To worsen voltage stability and raise electricity costs. D) To increase energy losses and reduce system capacity. Show Answer Correct Answer: A) To reduce energy losses, improve voltage stability, increase system capacity, and lower electricity costs. 35. The peak current read from an oscilloscope trace is 5.25 A. What is the rms current? A) 7.42 V. B) 3.71 A. C) 5.25 A. D) 2.63 A. Show Answer Correct Answer: B) 3.71 A. 36. Angular displacement per unit time is ..... A) Frequency. B) Angular frequency. C) All the above. D) None of the above. Show Answer Correct Answer: B) Angular frequency. 37. A material that allows electrons to flow freely. A) Semiconductor. B) Direct Current. C) Resistance. D) Electrical Conductor. Show Answer Correct Answer: D) Electrical Conductor. 38. Unit of angular frequency is ..... A) Degree. B) Degrees per second. C) Second. D) None of the above. Show Answer Correct Answer: B) Degrees per second. 39. What is the effect of inductive reactance on the current in an AC circuit? A) Inductive reactance allows current to flow freely without any phase shift. B) Inductive reactance has no effect on the current in an AC circuit. C) Inductive reactance causes the current to lag behind the voltage, reducing the overall current flow. D) Inductive reactance increases the current flow in the circuit. Show Answer Correct Answer: C) Inductive reactance causes the current to lag behind the voltage, reducing the overall current flow. 40. What is the relationship between frequency and capacitive reactance? A) No relationship. B) Inversely proportional. C) Directly proportional. D) Constant. Show Answer Correct Answer: B) Inversely proportional. 41. Reactive power is always ..... A) Measured in ohms. B) 90$^\circ$ out of phase with true power. C) Equal to true power. D) Responsible for performing most of the work in a circuit. Show Answer Correct Answer: B) 90$^\circ$ out of phase with true power. 42. Which of the following is NOT a component of a three-pin plug? A) Live pin. B) Plastic pin. C) Neutral pin. D) Earth pin. Show Answer Correct Answer: B) Plastic pin. 43. The oscillations of a copper disc in a magnetic field are lightly damped because of A) Eddy Currents. B) Gravity. C) Inertia. D) None of these. Show Answer Correct Answer: A) Eddy Currents. 44. The impedance Z can be expressed as: A) $\frac{I_{rms}}{V_{rms}}$. B) $\frac{Vrms}{I_{rms}}$. C) $V_{rms}-I_{rms}$. D) $V_{rms}+I_{rms}$. Show Answer Correct Answer: B) $\frac{Vrms}{I_{rms}}$. 45. Which one of the below AC parameters show the effective Dc value? A) RMS value. B) Peak Value. C) Frequency. D) Peak to peak value. Show Answer Correct Answer: A) RMS value. 46. An Ac voltmeter connected with 50 Hz AC source it read 200 V, maximum voltage during periodic time will be . A) 28.2 V. B) 0.282 V. C) 282 V. D) 2.82 V. Show Answer Correct Answer: C) 282 V. 47. All of the following are electromagnetic waves EXCEPT A) Radio. B) Infra-red. C) Light. D) Sound. Show Answer Correct Answer: D) Sound. 48. Which of the following is a disadvantage of DC compared to AC in terms of voltage transformation? A) DC requires more complex infrastructure. B) DC is less stable than AC. C) DC cannot be easily transformed to different voltage levels. D) DC is more expensive to produce. Show Answer Correct Answer: C) DC cannot be easily transformed to different voltage levels. 49. A current is said to be alternating when it changes in A) Magnitude. B) Direction. C) Both 'a' and 'b'. D) None of these. Show Answer Correct Answer: C) Both 'a' and 'b'. 50. An inductance of 1 mH a condenser of 10 mF and a resistance of 50 W are connected in series. The reactances of inductor and condensers are same. The reactance of either of them will be ..... A) 3.2 W. B) 30 W. C) 100 W. D) 10 W. Show Answer Correct Answer: D) 10 W. 51. Which of these answer choices below is an example of how a Direct Current obtains its energy? A) Television. B) Computer. C) Battery. D) Lights. Show Answer Correct Answer: C) Battery. 52. The resistance of the primary coil of a well-designed, 1:10 step-down transformer is 1 W. With the secondary circuit open, the primary is connected to a 12 V ac generator. The primary current is: A) Essentially zero. B) About 12 A. C) About 120 A. D) Depends on the actual number of turns in the primary coil. Show Answer Correct Answer: A) Essentially zero. 53. AC generators used to produce alternating current by converting A) Kinetic energy into electrical energy. B) Kinetic energy into potential energy. C) Electrical energy into kinetic energy. D) Potential energy into electrical energy. Show Answer Correct Answer: A) Kinetic energy into electrical energy. 54. The alternating current can be measured with the help of A) Moving magnet galvanometer. B) Hot wire voltmeter. C) Hot wire ammeter. D) Suspended coil type galvanometer. Show Answer Correct Answer: C) Hot wire ammeter. 55. A series LCR circuit connected to an AC source is shown. Write the expression for the impedance offered by this circuit. A) $Z = \sqrt{R^2 + X_L^2 + X_C^2}$. B) $Z = \sqrt{R^2 + (X_L-X_C)^2}$. C) $Z = R$. D) $Z = R + (X_L-X_C)$. Show Answer Correct Answer: B) $Z = \sqrt{R^2 + (X_L-X_C)^2}$. 56. What is the function of a fuse in an AC household circuit? A) To convert AC to DC. B) To protect against overload. C) To increase current. D) To store energy. Show Answer Correct Answer: B) To protect against overload. 57. A power supply has a peak value of 433 Volts sine wave, what is the effective dc voltage of this power supply? A) 220 V. B) 612 V. C) 433 V. D) 306 V. Show Answer Correct Answer: D) 306 V. 58. Find the power loss in the line as heat A) 650 kW. B) 700 kW. C) 600 kW. D) 550 kW. Show Answer Correct Answer: C) 600 kW. ← PreviousRelated QuizzesScience QuizzesClass 12 QuizzesClass 12 Physics (Part I) Chapter 7 Alternating Current Quiz 1Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 2Class 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 8 🏠 Back to Homepage 📘 Download PDF Books 📕 Premium PDF Books