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 5 🏠 Homepage 📘 Download PDF Books 📕 Premium PDF Books Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 5 (60 MCQs) Quiz Instructions Select an option to see the correct answer instantly. 1. What is a key benefit of using transformers with AC? A) They can adjust voltage levels efficiently. B) They can store electrical energy. C) They can increase the frequency of AC. D) They can convert AC to DC. Show Answer Correct Answer: A) They can adjust voltage levels efficiently. 2. Current whose magnitude changes with time and direction reverses periodically A) AC. B) DC. C) Induced current. D) All of the above. Show Answer Correct Answer: A) AC. 3. What is the formula for impedance (Z) in an LCR circuit? A) Z = $\sqrt{R^2 + (X_L-X_c)^2}$. B) Z = R-(XL + Xc). C) $Z = R^2 + (XL + Xc)^2$. D) Z = R + (XL-Xc). Show Answer Correct Answer: A) Z = $\sqrt{R^2 + (X_L-X_c)^2}$. 4. What happens to the inductance when the magnetic field strength decreases? A) Increases. B) Decreases. C) Becomes zero. D) Remains the same. Show Answer Correct Answer: B) Decreases. 5. Impedance of RLC circuit at resonance is A) Maximum. B) Minimum. C) Equal to R. D) None of these. Show Answer Correct Answer: B) Minimum. 6. Which component is essential in a simple single-phase AC generator? A) Battery. B) Diode. C) Commutator. D) Rotor. Show Answer Correct Answer: D) Rotor. 7. The power that is distributed from a power plant to your home is: A) Low voltage to low voltage. B) High voltage to high voltage. C) Low voltage to high voltage. D) High voltage to low voltage. Show Answer Correct Answer: D) High voltage to low voltage. 8. If the phase difference is 0 degree, the circuit is purely ..... A) Capacitive. B) Resistive. C) Inductive. D) None of these. Show Answer Correct Answer: B) Resistive. 9. An electric fan is: A) An accelerator. B) Electric generator. C) Based on electromagnetic induction. D) Electric motor. Show Answer Correct Answer: D) Electric motor. 10. State whether the following statements is TRUE or FALSE;The magnitude of magnetic field of an electromagnetic wave does not depend on position (x). A) True. B) False. C) All the above. D) None of the above. Show Answer Correct Answer: B) False. 11. (d) A 100 W lamp is designed for use with 110 V ac What is the resistance of its filament? A) 0 ohm. B) 121ohms. C) 100ohms. D) 221ohms. Show Answer Correct Answer: B) 121ohms. 12. What is required to use an electric appliance? A) Connect it to a power plant. B) Use a solar cell. C) Use a fuel cell. D) Plug it into an outlet. Show Answer Correct Answer: D) Plug it into an outlet. 13. RMS stands for ..... A) Root mean Squared value. B) Remote Monitoring System. C) All the above. D) None of the above. Show Answer Correct Answer: A) Root mean Squared value. 14. What is the potential difference of alternating current in the UK? A) 230 volts. B) Cannot be determined. C) 50 Hertz. D) Not mentioned. Show Answer Correct Answer: A) 230 volts. 15. The opposition of a resistor to the alternating current flow is known as A) Inductive reactant. B) Capacitive reactant. C) Resistance. D) None of the above. Show Answer Correct Answer: C) Resistance. 16. Direction of induced current is determined by ..... A) Right hand thumb rule. B) Fleming's left hand rule. C) Fleming's right hand rule. D) Faraday's law. Show Answer Correct Answer: C) Fleming's right hand rule. 17. What happens to the value of voltage as the conductor travels from parallel to crossing the lines of force? A) It builds from 0 to a maximum positive value. B) It decreases steadily. C) It fluctuates randomly. D) It remains at zero. Show Answer Correct Answer: A) It builds from 0 to a maximum positive value. 18. What is the significance of the density of the magnetic flux in emf generation? A) It determines the color of the conductor. B) It only affects the speed of the conductor. C) It has no significance. D) It affects the amount of emf generated. Show Answer Correct Answer: D) It affects the amount of emf generated. 19. A power transmission line feeds power at 2200 V with a current of 5 A to a step-down transformer whose primary has 4000 turns. To obtain 220 V output, how many turns should be in the secondary? A) 4000 turns. B) 200 turns. C) 400 turns. D) 800 turns. Show Answer Correct Answer: C) 400 turns. 20. A pure inductor is connected to an a.c. source of frequency 100 Hz and the r.m.s. value of the voltage is 12 V. If the peak value of the current flowing through the inductor is 14 A, what is the inductance of the inductor? A) 30 mH. B) 1.9 mH. C) 1.6 mH. D) 39 mH. Show Answer Correct Answer: B) 1.9 mH. 21. Which factor increases rms value of current? A) Decrease in voltage. B) Increase in phase angle. C) Increase in peak voltage. D) Increase in impedance. Show Answer Correct Answer: C) Increase in peak voltage. 22. What is the relationship between frequency and the output voltage in an AC generator? A) Higher frequency results in lower voltage. B) Frequency has no effect on voltage. C) Higher frequency results in higher voltage. D) Voltage is constant regardless of frequency. Show Answer Correct Answer: C) Higher frequency results in higher voltage. 23. How can the 'ripples' in a smoothed output voltage graph be reduced? A) By using a larger capacitor. B) By increasing the peak voltage. C) By increasing the load resistance. D) By decreasing the frequency. Show Answer Correct Answer: A) By using a larger capacitor. 24. What are the conditions for resonance to occur in an RLC circuit? A) The circuit must have a resistor value of zero. B) Inductive reactance equals capacitive reactance (XL = XC) at the resonant frequency. C) Inductive reactance is always greater than capacitive reactance. D) Resonance occurs at any frequency regardless of reactance. Show Answer Correct Answer: B) Inductive reactance equals capacitive reactance (XL = XC) at the resonant frequency. 25. Describe the effect of capacitance on the phase angle in AC circuits. A) Capacitance causes the voltage to lead the current, decreasing the phase angle in AC circuits. B) Capacitance has no effect on the phase angle in AC circuits. C) Capacitance causes the current and voltage to be in phase, resulting in a phase angle of zero. D) Capacitance causes the current to lead the voltage, increasing the phase angle in AC circuits. Show Answer Correct Answer: D) Capacitance causes the current to lead the voltage, increasing the phase angle in AC circuits. 26. An alternating current is set up in an LRC circuit. For which of the following circuit elements are the current and voltage in phase? A) Inductor only. B) Resistor only. C) Capacitor only. D) Resistor and capacitor only. Show Answer Correct Answer: B) Resistor only. 27. What is the role of a rectifier in converting AC to DC? A) A rectifier converts DC to AC using transformers to increase voltage. B) A rectifier is used to amplify AC signals for better transmission. C) A rectifier converts AC to DC by allowing current to flow in one direction, using diodes to block reverse flow. D) A rectifier allows current to flow in both directions, enabling bidirectional flow. Show Answer Correct Answer: C) A rectifier converts AC to DC by allowing current to flow in one direction, using diodes to block reverse flow. 28. The unit of measurement of the ability of a capacitor to store an electrical charge is the A) Farad. B) Ohm. C) Amp. D) None of the above. Show Answer Correct Answer: A) Farad. 29. Which statement is correct for AC? A) Direction is constant. B) Magnitude is constant. C) Both change with time. D) Neither changes. Show Answer Correct Answer: C) Both change with time. 30. Inductance in an AC circuit causes the current to A) Lead the voltage. B) Lag the voltage. C) Remain in phase with the voltage. D) None of the above. Show Answer Correct Answer: B) Lag the voltage. 31. In pure resistive AC circuit, instantaneous value of voltage or current: A) Current lags behind voltage. B) Current leads voltage by 90. C) Both are in-phase. D) Voltage leads current by 90. Show Answer Correct Answer: C) Both are in-phase. 32. In a circuit containing R and L as the frequency of the impressed AC increases, the impedance of the circuit A) Decreases. B) Increases. C) Remains unchanged. D) First increases and then decreases. Show Answer Correct Answer: B) Increases. 33. What occurs when the conductor moves beyond 180$^\circ$? A) Emf remains constant. B) No emf is generated. C) The cycle stops. D) Emf builds from maximum positive to maximum negative. Show Answer Correct Answer: D) Emf builds from maximum positive to maximum negative. 34. Why is power factor correction important in electrical circuits? A) To increase energy losses and reduce efficiency. B) To make the system less reliable. C) To improve the efficiency of the system and reduce energy losses. D) To decrease the overall power output of the system. Show Answer Correct Answer: C) To improve the efficiency of the system and reduce energy losses. 35. In a pure inductive circuit, the resistance offered to current is calle A) Resistance. B) Inductive reactance. C) Capacitive reactance. D) Resistance and reactance. Show Answer Correct Answer: B) Inductive reactance. 36. Which current did Tesla believe was the better option? A) Direct current. B) Alternating current. C) All the above. D) None of the above. Show Answer Correct Answer: B) Alternating current. 37. Fill in the blank:Follicles will lie ..... in the skin. A) Shallower. B) Deeper. C) Thicker. D) Higher. Show Answer Correct Answer: A) Shallower. 38. What is the color of the live wire in a mains cable? A) Blue. B) Brown. C) Green. D) Yellow. Show Answer Correct Answer: B) Brown. 39. What is the purpose of the National Grid? A) To store electricity. B) To distribute electricity efficiently. C) To convert electricity to heat. D) To generate electricity. Show Answer Correct Answer: B) To distribute electricity efficiently. 40. The power factor is the ratio of ..... power to ..... power. A) True and apparent. B) True and real. C) Positive and negative. D) Factor and real. Show Answer Correct Answer: A) True and apparent. 41. An LCR series circuit connected to a source E is at resonance. Then the voltage across A) L equals applied voltage. B) C is zero. C) R is zero. D) R equals applied voltage. Show Answer Correct Answer: D) R equals applied voltage. 42. "The direction of an induced e.m.f. is always such that it tends to set up a current opposing the motion or the change of flux responsible for inducing that e.m.f." , this is the statement for? A) Lenz's law. B) Faraday's law. C) Fleming's right hand rule. D) Fleming's left hand rule. Show Answer Correct Answer: A) Lenz's law. 43. In an AC circuit, if the voltage is given by v=10.0 sin(1000t), what is the rms voltage? A) 7.07 V. B) 5.0 V. C) 10.0 V. D) 14.14 V. Show Answer Correct Answer: A) 7.07 V. 44. The potential difference between two conductors which are insulated from each other is measured in A) Volts. B) Amperes. C) Coulombs. D) None of the above. Show Answer Correct Answer: A) Volts. 45. Explain how an oscilloscope can be used to visualize AC signals. A) An oscilloscope visualizes AC signals by displaying their waveforms on a screen, showing amplitude and frequency over time. B) An oscilloscope measures temperature changes in AC signals. C) An oscilloscope amplifies AC signals for better sound quality. D) An oscilloscope converts AC signals into digital audio formats. Show Answer Correct Answer: A) An oscilloscope visualizes AC signals by displaying their waveforms on a screen, showing amplitude and frequency over time. 46. Most of the electrical energy sold by power companies is transmitted and distributed as A) (a) AC power. B) (b) DC power. C) All the above. D) None of the above. Show Answer Correct Answer: A) (a) AC power. 47. What is the difference between the movement of the two electrons between the two types of currents? A) There's no difference. B) An Alternating Currents electrons move in one direction while a Direct Currents electrons move back and forth. C) An Alternating Currents electrons move back and forth while a Direct Currents electrons move in one direction. D) An Alternating Currents electrons move back and forth while a Direct Currents electrons don't move at all. Show Answer Correct Answer: C) An Alternating Currents electrons move back and forth while a Direct Currents electrons move in one direction. 48. In a series resonant circuit, the impedance of the circuit is A) Minimum. B) Maximum. C) Zero. D) None of the above. Show Answer Correct Answer: A) Minimum. 49. An A.C. voltmeter reads 250 volts. The frequency of alternating is 50 Hz, the peak value of voltage is A) 3.535 volts. B) 3525.0 volts. C) 35.35 volts. D) 353.5 volts. Show Answer Correct Answer: D) 353.5 volts. 50. What is the relationship between inductive reactance (XL) and frequency? A) XL is constant. B) XL is independent of frequency. C) XL increases with frequency. D) XL decreases with frequency. Show Answer Correct Answer: C) XL increases with frequency. 51. In a pure capacitor circuit, ..... A) The current leads voltage by $\frac{\pi}{2}$. B) The current and voltage are in phase. C) The voltage leads current by $\frac{\pi}{2}$. D) The current and voltage are in antiphase. Show Answer Correct Answer: A) The current leads voltage by $\frac{\pi}{2}$. 52. What is the formula for series impedance in an RLC circuit? A) $Z=R+\left(X_L+X_C\right)$. B) $Z=\sqrt{R^2+\left(X_L-X_C\right)^2}$. C) $Z=R^2+\left(X_L-X_C\right)^2$. D) None of the above. Show Answer Correct Answer: B) $Z=\sqrt{R^2+\left(X_L-X_C\right)^2}$. 53. A bulb and a capacitor are connected in series to a source of alternating current. If its frequency is increased, while keeping the voltage of the source constant, then bulb will A) Give less intense light. B) Give more intense light. C) Give light of same intensity before. D) Stop radiating light. Show Answer Correct Answer: B) Give more intense light. 54. How is impedance different from resistance in an AC circuit? A) Impedance only includes reactance in an AC circuit. B) Impedance is not relevant in an AC circuit. C) Impedance is the same as resistance in an AC circuit. D) Impedance includes both resistance and reactance. Show Answer Correct Answer: D) Impedance includes both resistance and reactance. 55. Alternating current changes A) Only direction but not magnitude. B) Does not change anything. C) Its magnitude as well as direction. D) Only magnitude but not direction. Show Answer Correct Answer: C) Its magnitude as well as direction. 56. What is the effect of increasing the strength of the magnetic field on the emf generated? A) It decreases the emf. B) It increases the emf. C) It has no effect. D) It only affects the frequency. Show Answer Correct Answer: B) It increases the emf. 57. What is the difference between step-up and step-down transformers? A) Step-up transformers increase voltage; step-down transformers decrease voltage. B) Both transformers increase voltage but differ in size. C) Step-up transformers decrease voltage; step-down transformers increase voltage. D) Step-up transformers convert AC to DC; step-down transformers convert DC to AC. Show Answer Correct Answer: A) Step-up transformers increase voltage; step-down transformers decrease voltage. 58. The primary winding of a transformer has 100 turns and its secondary winding has 200 turns. The primary is connected to an AC supply of 120V and the current flowing in it is 10A. The voltage and the current in the secondary are A) 120V, 20A. B) 240V, 10A. C) 60V, 20A. D) 240V, 5A. Show Answer Correct Answer: D) 240V, 5A. 59. What role do transformers play in reducing energy losses in AC systems? A) They convert AC to DC to reduce losses. B) They allow for high-voltage transmission, which reduces current and losses. C) They increase the frequency of AC to reduce losses. D) They store excess energy to reduce losses. Show Answer Correct Answer: B) They allow for high-voltage transmission, which reduces current and losses. 60. The behavior of resistance in pure resistor is frequency A) Dependent. B) Independent. C) No response. D) None of these. Show Answer Correct Answer: B) Independent. ← PreviousNext →Related 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 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 9 🏠 Back to Homepage 📘 Download PDF Books 📕 Premium PDF Books