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 4 🏠 Homepage 📘 Download PDF Books 📕 Premium PDF Books Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 4 (60 MCQs) Quiz Instructions Select an option to see the correct answer instantly. 1. What is the effect of increasing frequency on the impedance of a capacitor? A) Increasing frequency increases the impedance of a capacitor. B) Increasing frequency decreases the impedance of a capacitor. C) Impedance of a capacitor is constant regardless of frequency. D) Increasing frequency has no effect on the impedance of a capacitor. Show Answer Correct Answer: B) Increasing frequency decreases the impedance of a capacitor. 2. Explain the concept of resonance in AC circuits. A) Resonance occurs when the circuit is short-circuited. B) Resonance happens only in DC circuits. C) Resonance in AC circuits is the condition where inductive and capacitive reactances are equal, resulting in maximum current at the resonant frequency. D) Resonance is the point where resistance is minimized in a circuit. Show Answer Correct Answer: C) Resonance in AC circuits is the condition where inductive and capacitive reactances are equal, resulting in maximum current at the resonant frequency. 3. In which circuit voltage leads current? A) Pure inductor. B) Pure capacitor. C) Pure resistor. D) Resonant RLC. Show Answer Correct Answer: B) Pure capacitor. 4. Sharpness is more when A) R is large. B) R is small. C) XL is small. D) Bandwidth is large. Show Answer Correct Answer: B) R is small. 5. AC generators works based on A) Newton's Law. B) Faraday's Law. C) Electrostatic law. D) Lenz Law. Show Answer Correct Answer: B) Faraday's Law. 6. An AC power supply is giving 120 Vrms, what is the average DC voltage for this power supply? A) 169.7 V. B) 100 V. C) 120 V. D) 220 V. Show Answer Correct Answer: C) 120 V. 7. A wall socket in Europe gives 120V RMS voltage, What is the peak voltage used in Europe? A) 89 V. B) 220 V. C) 120 V. D) 170 V. Show Answer Correct Answer: D) 170 V. 8. Frequency is 1/period and period is 1/frequency? True or false? A) YEA baby. B) Not until i meet you. C) Only when the moon is full. D) None of the above. Show Answer Correct Answer: A) YEA baby. 9. Peak-to-peak, Peak, RMS, and Average are four forms of measurement of voltage and current associated with sine waves. A) True. B) False. C) All the above. D) None of the above. Show Answer Correct Answer: A) True. 10. Advantages of DC are A) Most equipment are more efficient when directly powered from DC. B) Less risks of shock hazard for voltages below 48 Volts. C) More efficient. D) All the above. Show Answer Correct Answer: D) All the above. 11. What is the main characteristic of alternating current? A) It is used in flashlights. B) It is provided by batteries. C) It flows in one direction. D) It reverses direction. Show Answer Correct Answer: D) It reverses direction. 12. How does AC differ from direct current (DC)? A) AC is always more efficient than DC. B) DC can be transmitted over long distances without loss. C) AC is used exclusively in batteries. D) AC differs from DC in that it alternates direction, while DC flows in one direction. Show Answer Correct Answer: D) AC differs from DC in that it alternates direction, while DC flows in one direction. 13. What is the role of a capacitor in an AC circuit? A) A capacitor converts AC to DC in an AC circuit. B) A capacitor acts as a resistor to limit current flow in an AC circuit. C) A capacitor stores energy, smooths voltage fluctuations, and introduces phase shifts in an AC circuit. D) A capacitor generates electrical power in an AC circuit. Show Answer Correct Answer: C) A capacitor stores energy, smooths voltage fluctuations, and introduces phase shifts in an AC circuit. 14. Magnetic flux of 5 mwb is linked with a coil, when current of 1 mA flows through it, Self-inductance will be A) 1 H. B) 50 H. C) 20 H. D) 5 H. Show Answer Correct Answer: D) 5 H. 15. An electrical element X when connected to an alternating voltage source has current through it leading the voltage by 2radian. Identify X A) Inductor. B) Capacitor. C) Series LR circuit. D) Resistor. Show Answer Correct Answer: B) Capacitor. 16. What is the condition for RCL circuit to oscillate at resonant frequency? A) R & X$_{C }$must be equal. B) X$_{C}$ & X$_{L}$ must be equal. C) R, X$_{C}$ & X$_{L}$ must be equal. D) R & X$_{L}$ must be equal. Show Answer Correct Answer: B) X$_{C}$ & X$_{L}$ must be equal. 17. Choose the wrong statement about the power of an ac circuit A) There are no power dissipated in capacitor and inductor. B) Power is only dissipated in resistor. C) The ratio of real power to apparent power is called the power factor. D) At resonance, power factor is equal to real power. Show Answer Correct Answer: D) At resonance, power factor is equal to real power. 18. If the vector diagram of two AC waveforms is a right angle, then the waves ..... A) Have the same peak voltage. B) Are 90$^\circ$ out of phase. C) Are in phase. D) Have the same frequency. Show Answer Correct Answer: B) Are 90$^\circ$ out of phase. 19. In a pure inductive circuit, the phase angle between current and emf. A) 90$^\circ$. B) 120$^\circ$. C) 60$^\circ$. D) 45$^\circ$. Show Answer Correct Answer: A) 90$^\circ$. 20. The term that describes the combined resistive forces in an ac circuit is A) Resistance. B) Reactance. C) Impedance. D) None of the above. Show Answer Correct Answer: C) Impedance. 21. Explain the concept of impedance in AC circuits. A) Impedance is the measure of voltage in a circuit. B) Impedance is the total opposition to AC current flow in a circuit, combining resistance and reactance. C) Impedance is the speed of current flow in a circuit. D) Impedance is only the resistance in a circuit. Show Answer Correct Answer: B) Impedance is the total opposition to AC current flow in a circuit, combining resistance and reactance. 22. High frequency oscillations refer to the frequency of the wave length and the number of cycles completed per second. A) True. B) False. C) All the above. D) None of the above. Show Answer Correct Answer: A) True. 23. On the oscilloscope the time is represented on A) Not represented on the scope. B) The horizontal axis. C) The sine of the angle. D) The vertical axis. Show Answer Correct Answer: B) The horizontal axis. 24. Condition for resonance A) XL = XC. B) XL = 2XC. C) XL =1/XC. D) XC = 1/XL. Show Answer Correct Answer: A) XL = XC. 25. In LCR series ac circuit, the current A) Is always in phase with the voltage. B) Always lags the generator voltage. C) Always leads the generator voltage. D) None of these. Show Answer Correct Answer: D) None of these. 26. Milli Amps equals A) 1000 A. B) 0.001 A. C) 0.1 A. D) 10 A. Show Answer Correct Answer: B) 0.001 A. 27. In the case of phasor diagram, the vector rotates A) Clockwise. B) Anti-clockwise. C) Remain stationary. D) None. Show Answer Correct Answer: B) Anti-clockwise. 28. When capacitors are connected in parallel, the total capacitance is equal to A) The sum of the reciprocals of the capacitances. B) The sum of the capacitances divided by the number of capacitors. C) The sum of the capacitances. D) None of the above. Show Answer Correct Answer: C) The sum of the capacitances. 29. A transformer is used to light a 100 W and 100 V lamp from a 220 V mains. If the main current is 0.5 A, the efficiency of the transformer is approximately A) 30%. B) 10%. C) 50%. D) 90%. Show Answer Correct Answer: D) 90%. 30. Which type of current is used in batteries 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). 31. What is the difference between series and parallel resonance? A) Parallel resonance results in maximum current flow. B) The main difference is that series resonance maximizes current while parallel resonance maximizes voltage. C) Series resonance and parallel resonance have the same effect on circuit behavior. D) Series resonance is used for high voltage applications. Show Answer Correct Answer: B) The main difference is that series resonance maximizes current while parallel resonance maximizes voltage. 32. Poor power factor A) Reduces load handling capability of electrical system. B) Results in more power losses in electrical system. C) Results in less power losses in electrical system. D) Overloads the power supply. Show Answer Correct Answer: B) Results in more power losses in electrical system. 33. What is the relationship between RMS current and peak current? A) Irms = Imax x 0.5. B) Irms = Imax x 2. C) Irms = Imax x 0.707. D) Irms = Imax x 1.414. Show Answer Correct Answer: C) Irms = Imax x 0.707. 34. What does AC stand for in electrical terms? A) Alternating Current. B) Active Current. C) Applied Current. D) Absolute Current. Show Answer Correct Answer: A) Alternating Current. 35. How much inductance should be connected to 100V, 50Hz AC supply so that a maximum current of 0.45A flows through it A) 1 H. B) 10 H. C) 5 H. D) 15 H. Show Answer Correct Answer: A) 1 H. 36. The electricity in our house is A) AC. B) DC. C) AD. D) BC. Show Answer Correct Answer: A) AC. 37. What is the purpose of a rectifier in an AC system? A) To amplify the AC signal. B) To filter out noise from the AC signal. C) To store energy in the AC system. D) The purpose of a rectifier in an AC system is to convert AC to DC. Show Answer Correct Answer: D) The purpose of a rectifier in an AC system is to convert AC to DC. 38. The instantaneous current in an ac circuit is i=2.0 sin314t, what is rms value of the current. A) 2 A. B) 1.414 A. C) 2.828A. D) 1 A. Show Answer Correct Answer: B) 1.414 A. 39. X-ray photographs show softer tissue A) The same as dense bones. B) As bright white areas. C) As dark, highly exposed areas. D) As invisible. Show Answer Correct Answer: C) As dark, highly exposed areas. 40. What is the opposition to AC by a capacitor called? A) Capacitive Reactance. B) Impedance. C) Inductive Reactance. D) Resistance. Show Answer Correct Answer: A) Capacitive Reactance. 41. Power dissipation in pure inductive or in a pure capacitive circuit is: A) Minimum. B) Infinite. C) Zero. D) Maximum. Show Answer Correct Answer: C) Zero. 42. Which circuit can act as a radio tuner? A) R and L. B) R and C. C) L and C. D) R and diode. Show Answer Correct Answer: C) L and C. 43. A sine wave has a peak value of 354 V, What is the RMS value? A) 200V. B) 500 V. C) 250 V. D) 354 V. Show Answer Correct Answer: C) 250 V. 44. The root mean square value of AC depends upon A) Only on peak value. B) Only on the frequency of the wave. C) Only on instantaneous value of the wave. D) All of the above. Show Answer Correct Answer: A) Only on peak value. 45. A circuit has a peak voltage of 275V. What is the average voltage value? A) 175V. B) 277V. C) 190V. D) 120V. Show Answer Correct Answer: A) 175V. 46. Which of the following in the carrier wave remains constant in frequency modulation (FM)? A) Amplitude. B) Displacement. C) Wavelength. D) Speed. Show Answer Correct Answer: D) Speed. 47. All of the following have the same units except: A) Inductance. B) Impedance. C) Capacitive reactance. D) Resistance. Show Answer Correct Answer: A) Inductance. 48. In which case average power is zero? A) Pure inductor. B) RL circuit. C) Pure resistor. D) Resonant circuit. Show Answer Correct Answer: A) Pure inductor. 49. Which wire is connected to the earth pin in a plug? A) Live wire. B) Neutral wire. C) Earth wire. D) None. Show Answer Correct Answer: C) Earth wire. 50. Which device is used to generate AC power in a power station? A) Generator. B) Battery. C) Rectifier. D) Transformer. Show Answer Correct Answer: A) Generator. 51. The potential difference V and the current i flowing through an instrument in an ac circuit of frequency f are given by V=5 cos wt volts and I = 2 sin wt amperes (where w = 2pf). The power dissipated in the instrument is A) 10W. B) 5W. C) Zero. D) 2.5W. Show Answer Correct Answer: C) Zero. 52. What is the relationship between phase difference and impedance? A) Phase difference has no effect on impedance. B) Impedance is solely determined by resistance, not phase difference. C) The phase difference is directly related to the impedance, with higher reactance causing greater phase differences. D) Higher impedance always results in lower phase differences. Show Answer Correct Answer: C) The phase difference is directly related to the impedance, with higher reactance causing greater phase differences. 53. The symbol for impedance is A) L. B) X. C) Z. D) None of the above. Show Answer Correct Answer: C) Z. 54. What is the main advantage of using the National Grid? A) It generates electricity. B) It reduces electricity costs. C) It allows efficient transfer of electricity. D) It stores electricity for later use. Show Answer Correct Answer: C) It allows efficient transfer of electricity. 55. The following statement describe about an inductance except ..... A) It is the opposition that a substance offer to the current flow. B) Represented by L. C) Standard unit is Henry. D) Current always lagging voltage. Show Answer Correct Answer: A) It is the opposition that a substance offer to the current flow. 56. Measuring AC voltage by multimeter should A) Need to consider the polarity. B) No need to consider the polarity. C) Need to install in series. D) None of the above. Show Answer Correct Answer: B) No need to consider the polarity. 57. Sources of direct Current are A) DC generators and Batteries. B) DC power converters that rectify the AC. C) Solar panels. D) All the above. Show Answer Correct Answer: D) All the above. 58. Phase difference between voltage and current in pure resistor is: A) 90$^\circ$. B) 180$^\circ$. C) 45$^\circ$. D) 0$^\circ$. Show Answer Correct Answer: D) 0$^\circ$. 59. Which one below is the definition of frequency? A) One complete positive and one complete negative part of the wave. B) Time taken to complete one cycle. C) Number of cycles in one second. D) Maximum value of the AC wave. Show Answer Correct Answer: C) Number of cycles in one second. 60. How does the ability to use high voltages in AC transmission affect energy efficiency? A) It has no effect on energy efficiency. B) It increases energy losses. C) It makes the system more complex. D) It decreases energy losses by reducing current. Show Answer Correct Answer: D) It decreases energy losses by reducing current. ← 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 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 9 🏠 Back to Homepage 📘 Download PDF Books 📕 Premium PDF Books