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 7 🏠 Homepage 📘 Download PDF Books 📕 Premium PDF Books Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 7 (60 MCQs) Quiz Instructions Select an option to see the correct answer instantly. 1. The instantaneous current in an ac circuit is i=2.0 sin 314t, what is its frequency? A) 50 Hz. B) 100 Hz. C) 75 Hz. D) 60 Hz. Show Answer Correct Answer: A) 50 Hz. 2. Explain the concept of resonance in an R.L.C series AC circuit. A) Resonance in an R.L.C series AC circuit is the condition where inductive and capacitive reactances are equal, resulting in maximum current at the resonant frequency. B) Resonance happens at any frequency regardless of reactance values. C) Resonance is achieved when the resistance is minimized in the circuit. D) Resonance occurs when the circuit is disconnected from the power source. Show Answer Correct Answer: A) Resonance in an R.L.C series AC circuit is the condition where inductive and capacitive reactances are equal, resulting in maximum current at the resonant frequency. 3. Which of these will cause the resistance of a conductor to decrease? A) Decrease the length of the cross-sectional area. B) Decrease the length or increase the cross-sectional area. C) Increase the length or decrease the cross-sectional area. D) None of the above. Show Answer Correct Answer: B) Decrease the length or increase the cross-sectional area. 4. A coil has L= 0.04 H and R = 12 $\Omega$ when it is connected to 220 V. 50 Hz supply the current flowing through the coil, in amperes is A) 10.7. B) 14.7. C) 12.7. D) 11.7. Show Answer Correct Answer: C) 12.7. 5. Which of the following is NOT a common AC household component? A) Television. B) Electric fan. C) Light bulb. D) Car engine. Show Answer Correct Answer: D) Car engine. 6. How can the frequency of an alternating current be calculated using an oscilloscope trace? A) By measuring the resistance of the circuit. B) By measuring the current direction. C) By measuring the height of the peak. D) By measuring the time between two peaks. Show Answer Correct Answer: D) By measuring the time between two peaks. 7. In AC generator, maximum emf generated at an angle of A) 0 and 90. B) 90 and 180. C) 90 and 270. D) 180 and 360. Show Answer Correct Answer: C) 90 and 270. 8. The opposition of an inductor 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: A) Inductive reactant. 9. On the oscilloscope the vertical axis represents A) Power. B) Time. C) Voltage. D) Frequency. Show Answer Correct Answer: C) Voltage. 10. The alternating current from a source is represented by I= 0.5sin314t. The frequency of ac is A) Zero. B) 100Hz. C) 50Hz. D) 314Hz. Show Answer Correct Answer: C) 50Hz. 11. The value of power factor for a purely resistive circuit A) Phi. B) 1. C) -1. D) 0. Show Answer Correct Answer: B) 1. 12. Consider the following statements and then select the correct Statements A) I is correct, II and III are incorrect. B) I III are correct, II is incorrect. C) I II are correct, III is incorrect. D) I, II and III are correct. Show Answer Correct Answer: D) I, II and III are correct. 13. In a step-up transformer, the turns ratio $N_{p}:N_{s}$ $1:10$ $230\, \text{V}$ $2\, \text{A}$ A) $2\, \text{A}$. B) $0.2\, \text{A}$. C) $10\, \text{A}$. D) $20\, \text{A}$. Show Answer Correct Answer: D) $20\, \text{A}$. 14. What is the duration of one cycle known as ..... A) Instantaneous value. B) Period. C) Peak value. D) Waveform. Show Answer Correct Answer: B) Period. 15. The household line voltage of ac measured is $220\, \text{V}$ A) $220\, \text{V}$. B) $311\, \text{V}$. C) $155\, \text{V}$. D) $440\, \text{V}$. Show Answer Correct Answer: B) $311\, \text{V}$. 16. Which component in an AC circuit is used to change the voltage level? A) Transformer. B) Capacitor. C) Resistor. D) Inductor. Show Answer Correct Answer: A) Transformer. 17. Which of the following is a disadvantage of a single-phase system compared to a three-phase system? A) Higher efficiency. B) More complex design. C) Requires more conductors. D) Less power capacity. Show Answer Correct Answer: D) Less power capacity. 18. In an AC circuit, if the voltage is given by v=8.0 sin(500t), what is the peak voltage? A) 8.0 V. B) 16 V. C) 0 V. D) 4.0 V. Show Answer Correct Answer: A) 8.0 V. 19. Which of the following statements is correct about the phase lagging in a capacitive circuit? A) Voltage leads the current. B) Voltage leads the resistance. C) Current leads the voltage. D) Resistance leads the current. Show Answer Correct Answer: C) Current leads the voltage. 20. Apa yang terjadi apabila Xl lebih nesar dari pada Xc A) Rangkaian akan bersifat sepertiinduktor. B) Rangkaian akan bersifat seperti resistor. C) Rangkaian akan bersifat sepertikapasitor. D) Rangkaian akan bersifat sepertiisolator. Show Answer Correct Answer: A) Rangkaian akan bersifat sepertiinduktor. 21. Resonance happens in the AC circuit when this condition met ..... A) R=0. B) X$_{L}$= X$_{c}$. C) X$_{L}$= R. D) X$_{c}$= R. Show Answer Correct Answer: B) X$_{L}$= X$_{c}$. 22. If a student touches a live AC wire with wet hands, what could happen and why? A) The student could get a severe electric shock because water increases conductivity. B) The student will only feel a mild tingling. C) The student will be protected by the wire insulation. D) Nothing will happen because AC is safe. Show Answer Correct Answer: A) The student could get a severe electric shock because water increases conductivity. 23. At resonance RLC series circuit shows the behavior of: A) Pure inductive circuit. B) Pure RLC circuit. C) Pure resistive circuit. D) Pure capacitive circuit. Show Answer Correct Answer: C) Pure resistive circuit. 24. The AC voltage waveform is in the positive direction for some period of time and in the negative direction for some period of time. What is the name given to this waveform? A) Sine wave. B) Inverted wave. C) Hertz wave. D) Alternating wave. Show Answer Correct Answer: A) Sine wave. 25. Define root mean square (RMS) voltage. A) RMS voltage is the average of instantaneous voltages over one cycle. B) RMS voltage is the peak voltage divided by the square root of two. C) RMS voltage is the maximum voltage in a circuit. D) RMS voltage is the square root of the average of the squares of instantaneous voltages over one cycle. Show Answer Correct Answer: D) RMS voltage is the square root of the average of the squares of instantaneous voltages over one cycle. 26. The value of source frequency for which current amplitude is maximum A) 663.48Hz. B) 222.32 Hz. C) 770Hz. D) 550.52 Hz. Show Answer Correct Answer: A) 663.48Hz. 27. Define RMS current in the context of AC circuits. A) RMS current is the effective value of an AC current that delivers the same power as a DC current. B) RMS current is the maximum current that can flow in a circuit. C) RMS current is the peak value of an AC current. D) RMS current is the average value of an AC current over time. Show Answer Correct Answer: A) RMS current is the effective value of an AC current that delivers the same power as a DC current. 28. At what angles is the maximum emf generated during the rotation of a conductor? A) 45$^\circ$ and 135$^\circ$. B) 180$^\circ$ and 360$^\circ$. C) 90$^\circ$ and 270$^\circ$. D) 0$^\circ$ and 180$^\circ$. Show Answer Correct Answer: C) 90$^\circ$ and 270$^\circ$. 29. ASSERTION:IRON LOSS IS MINIMIZED USING LAMINATED COREREASON:LAMINATION OF CORE REDUCES EDDY CURRENTS A) BOTH ASSERTION AND REASON ARE TRUE AND REASON IS THE CORRECT EXPLANATION OF THE ASSERTION. B) BOTH ASSERTION AND REASON ARE TRUE AND REASON IS NOT THE CORRECT EXPLANATION OF THE ASSERTION. C) ASSERTION IS TRUE BUT REASON IS FALSE. D) ASSERTION AND REASON IS FALSE. Show Answer Correct Answer: A) BOTH ASSERTION AND REASON ARE TRUE AND REASON IS THE CORRECT EXPLANATION OF THE ASSERTION. 30. In an ac circuit, the effective voltage is A) Equal to the maximum instantaneous voltage. B) Greater than the maximum instantaneous voltage. C) Less than the maximum instantaneous voltage. D) None of the above. Show Answer Correct Answer: C) Less than the maximum instantaneous voltage. 31. What is phase difference between voltage and current in LCR series circuit at resonance? A) 90$^{o}$. B) 0$^{o}$. C) 30$^{o }$. D) 45$^{o }$. Show Answer Correct Answer: B) 0$^{o}$. 32. An ac circuit consists of an inductor of inductance 0.5 H and a capacitor of capacitance 8 mF in series. The current in the circuit is maximum when the angular frequency of ac source is A) 4000 rad/sec. B) 5000 rad/sec. C) 500 rad/sec. D) 2 x 10$^{5}$ rad/sec. Show Answer Correct Answer: C) 500 rad/sec. 33. How does the frequency of an AC signal affect the reactance of a capacitor? A) Higher frequency increases reactance. B) The frequency of an AC signal inversely affects the reactance of a capacitor; higher frequency results in lower reactance. C) Lower frequency results in higher capacitance. D) Reactance is unaffected by frequency changes. Show Answer Correct Answer: B) The frequency of an AC signal inversely affects the reactance of a capacitor; higher frequency results in lower reactance. 34. Which EM wave has the longest wavelength? A) Blue light waves. B) Infrared waves. C) Radio waved. D) Gama waves. Show Answer Correct Answer: C) Radio waved. 35. The maximum instantaneous value measured from zero value is known as? A) Cycle. B) Peak to peak value. C) Period. D) Peak value. Show Answer Correct Answer: D) Peak value. 36. What does RMS stand for in electrical terms? A) Root Mean Standard. B) Relative Mean Square. C) Radial Mean Square. D) Root Mean Square. Show Answer Correct Answer: D) Root Mean Square. 37. What does the term 'amplitude' refer to in an AC waveform? A) The time taken for one complete cycle. B) The number of cycles per second. C) The phase difference between two waveforms. D) The maximum voltage or current value. Show Answer Correct Answer: D) The maximum voltage or current value. 38. What is the role of the neutral wire in a circuit? A) To connect the appliance to the earth. B) To increase the voltage. C) To carry current to the appliance. D) To carry current away from the appliance. Show Answer Correct Answer: D) To carry current away from the appliance. 39. The true power in a circuit with a current of 4A that passes through a 50$\Omega$ resistor is ..... A) 400W. B) 200W. C) 600W. D) 800W. Show Answer Correct Answer: D) 800W. 40. What is the voltage stepped up to for transmission across the UK? A) 500, 000 volts (500kV). B) 600, 000 volts (600kV). C) 300, 000 volts (300kV). D) 400, 000 volts (400kV). Show Answer Correct Answer: D) 400, 000 volts (400kV). 41. Which one of the below is NOT an AC device? A) Drill machine. B) Microwave. C) Fridge. D) Washing machine. Show Answer Correct Answer: A) Drill machine. 42. AC is preferred over DC because A) AC voltages can be easily and efficiently converted from one voltage to the other by means of transformers. B) Electrical energy (AC)can be transmitted economically over long distances. C) AC circuits exhibit characteristics which are exploited in many devices of daily use. D) All the above. Show Answer Correct Answer: D) All the above. 43. In a series LCR circuit voltages across resistor, Capacitor and Inductor are 10 V, 10 V and 20 V respectively. The source voltage is A) $10\sqrt{2}$. B) 40 V. C) $10\sqrt{6}$. D) 20 V. Show Answer Correct Answer: A) $10\sqrt{2}$. 44. Define the term 'peak voltage' in the context of AC. A) The voltage level at which AC frequency peaks. B) The minimum voltage level in an AC waveform. C) The maximum voltage level in an AC waveform. D) The average voltage level in an AC waveform. Show Answer Correct Answer: C) The maximum voltage level in an AC waveform. 45. What is the phase difference between current and voltage when a capacitor is connected to ac voltage? A) 60. B) 90. C) 0. D) 180. Show Answer Correct Answer: B) 90. 46. Instantaneous power is defined as A) The product of instantaneous current and voltage. B) The product of rms current and voltage. C) The product of peak current and voltage. D) Specific power. Show Answer Correct Answer: A) The product of instantaneous current and voltage. 47. What is the voltage at any particular point in an alternating current called? A) Average value. B) Peak value. C) Peak-to-peak value. D) Instantaneous value. Show Answer Correct Answer: D) Instantaneous value. 48. How does the transformer work with AC? A) A transformer uses thermal conduction to transfer energy. B) A transformer only works with DC current. C) A transformer generates electricity without any coils. D) A transformer works with AC by using electromagnetic induction to transfer energy between coils. Show Answer Correct Answer: D) A transformer works with AC by using electromagnetic induction to transfer energy between coils. 49. State whether the following statements is TRUE or FALSE; An electromagnetic wave consists of electric and magnetic fields. A) TRUE. B) FALSE. C) All the above. D) None of the above. Show Answer Correct Answer: A) TRUE. 50. The function of a generator is to change ..... A) Electrical energy to chemical energy. B) Mechanical energy to electrical energy. C) Electrical energy to mechanical energy. D) Chemical energy to electrical energy. Show Answer Correct Answer: B) Mechanical energy to electrical energy. 51. What is the standard frequency of AC in most countries? A) 50 Hz or 60 Hz. B) 40 Hz. C) 70 Hz. D) 100 Hz. Show Answer Correct Answer: A) 50 Hz or 60 Hz. 52. Which type of current is used in torches A) Alternating Current (AC). B) Direct Current (DC). C) All the above. D) None of the above. Show Answer Correct Answer: B) Direct Current (DC). 53. According to the power triangle, the apparent power is ..... A) Equal to the reactive power. B) Less than the reactive power. C) Greater than the true power. D) Less than the true power. Show Answer Correct Answer: C) Greater than the true power. 54. The value of current flowing through the resistor connected in the secondary A) 0.6 A. B) 3A. C) 2 A. D) 0.2 A. Show Answer Correct Answer: D) 0.2 A. 55. The electric mains supply in our homes and offices is a voltage that varies like a sine function with time such a voltage is called A and the current driven by it in a circuit is called the B.Here, A and B refer to A) AC voltage, AC current. B) AC voltage, DC current. C) DC voltage, AC current. D) AC voltage, DC voltage. Show Answer Correct Answer: A) AC voltage, AC current. 56. Apparent value of ac is A) Mean value for full cycle. B) Mean value for half cycle. C) Rms value. D) All. Show Answer Correct Answer: C) Rms value. 57. How many times per second does alternating current change direction? A) 120 times. B) 60 times. C) 30 times. D) 90 times. Show Answer Correct Answer: B) 60 times. 58. Which of the following statements about a series RCL circuit is true? A) At resonance, the total reactance and total resistance are equal. B) The impedance at resonance is purely inductive. C) The current flowing in the circuit at resonance is at maximum. D) The impedance at resonance is at maximum. Show Answer Correct Answer: C) The current flowing in the circuit at resonance is at maximum. 59. In alternating current equation, $I=I_o\\sin\\omega t$ $I_o$ A) Instantaneous current. B) RMS current. C) Peak current. D) Lowest current. Show Answer Correct Answer: C) Peak current. 60. What is the reactance for inductor? A) 1/wL. B) 1/wC. C) WC. D) WL. Show Answer Correct Answer: D) WL. ← 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 5Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 6Class 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