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 2 🏠 Homepage 📘 Download PDF Books 📕 Premium PDF Books Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 2 (60 MCQs) Quiz Instructions Select an option to see the correct answer instantly. 1. What is the phase relationship between the current and voltage in a purely capacitive circuit? A) The current leads the voltage by 90$^\circ$. B) The current lags the voltage by 90$^\circ$. C) The current leads the voltage by 0$^\circ$. D) None of the above. Show Answer Correct Answer: A) The current leads the voltage by 90$^\circ$. 2. What is the primary use of a step-up transformer in an X-ray tube? A) To decrease voltage. B) To increase voltage. C) To stabilize current. D) To convert AC to DC. Show Answer Correct Answer: B) To increase voltage. 3. Radio receivers are also known as A) R-L circuits. B) L-C circuits. C) R-C circuits. D) R-L-C circuits. Show Answer Correct Answer: C) R-C circuits. 4. Find the maximum value of current when inductance of 2 H is connected to 300V, 50 Hz supply A) 2.224 V. B) 0.676 V. C) 1.512 V. D) 0.337 V. Show Answer Correct Answer: B) 0.676 V. 5. Why is it important to reduce current in power transmission lines? A) To increase the speed of electricity flow. B) To reduce energy losses due to resistance. C) To make the lines safer for birds. D) To allow for more electricity to be transmitted. Show Answer Correct Answer: B) To reduce energy losses due to resistance. 6. Quantity of charge can be measured in A) Coulombs (C). B) Joule (J). C) Time (s). D) Ampere (A). Show Answer Correct Answer: A) Coulombs (C). 7. What is the maximum value of current or voltage in a waveform called? A) Wavelength. B) Amplitude. C) Frequency. D) Period. Show Answer Correct Answer: B) Amplitude. 8. If an electric bulb is connected to an AC source, which of the following statement is true about the phase difference between the voltage across the bulb and current flowing in it? A) The voltage is leading the current. B) In phase. C) The current is leading the voltage. D) Not in phase. Show Answer Correct Answer: B) In phase. 9. What is alternating current (AC)? A) Direct current (DC) flows in one direction only. B) Alternating current (AC) is a type of battery. C) Alternating current (AC) is always constant and unchanging. D) Alternating current (AC) is an electric current that periodically reverses direction. Show Answer Correct Answer: D) Alternating current (AC) is an electric current that periodically reverses direction. 10. The current produced by AC generators is A) Negative current. B) Direct current. C) Fixed current. D) Alternative current. Show Answer Correct Answer: D) Alternative current. 11. In a pure capacitive circuit if the frequency of ac source is doubled, then its capacitive reactance will be A) Doubled. B) Halved. C) Remains same. D) Zero. Show Answer Correct Answer: B) Halved. 12. In order for a circuit to work you need to have A) A voltage source. B) A complete pathway with no breaks in the circuit. C) A resistor. D) A voltage source and a complete pathway with no breaks in the circuit. Show Answer Correct Answer: D) A voltage source and a complete pathway with no breaks in the circuit. 13. What is the primary purpose of the simulation mentioned in the text? A) To illustrate the properties of direct current. B) To demonstrate the heating effect of current. C) To show how alternating current EMF is produced. D) To explain the concept of resistance. Show Answer Correct Answer: C) To show how alternating current EMF is produced. 14. What is the term for the maximum current in an A.C. circuit?(Im means peak current) A) Im. B) Iav. C) Imax. D) Irms. Show Answer Correct Answer: A) Im. 15. What is an Autotransformer? A) A transformer with a single winding. B) A transformer with no windings. C) A transformer with 2 windings. D) None of the above. Show Answer Correct Answer: A) A transformer with a single winding. 16. For the circuit with C = 15 $\mu$F connected to a 220 V, 50 Hz source, calculate the rms and peak values of current in the circuit. A) I rms = 2.20 A, i m = 3.11 A. B) I rms = 1.04 A, i m = 1.47 A. C) I rms = 0.22 A, i m = 0.31 A. D) I rms = 0.71 A, i m = 1.00 A. Show Answer Correct Answer: B) I rms = 1.04 A, i m = 1.47 A. 17. A circuit contains a AC voltage source, a resistor, and another component. The voltage amplitude is held constant as the frequency is increased. The current in the circuit is observed to increase as the frequency is increased. What is the additional component in the circuit? A) Light Bulb. B) Capacitor. C) Resistor. D) Inductor. Show Answer Correct Answer: B) Capacitor. 18. What is resonance in the context of alternating current? A) Resonance happens when the circuit has only capacitive reactance. B) Resonance is when the circuit has no resistance. C) Resonance in the context of alternating current is when inductive and capacitive reactances cancel each other out, resulting in a purely resistive circuit. D) Resonance occurs when the circuit has only inductive reactance. Show Answer Correct Answer: C) Resonance in the context of alternating current is when inductive and capacitive reactances cancel each other out, resulting in a purely resistive circuit. 19. Fill in the blank:It is ineffective when treating distorted curved hair follicles compared to the ..... methods. A) Laser. B) Blend. C) Flash. D) Thermal. Show Answer Correct Answer: B) Blend. 20. The instantaneous voltage through a device of impedance 20ohm is e = 80 sin 100 $\pi$ A) 2.828 A. B) 3 A. C) 1.732 A. D) 4A. Show Answer Correct Answer: A) 2.828 A. 21. What is the phase difference between the current and voltage in a purely resistive AC circuit? A) 0$^\circ$. B) 45$^\circ$. C) 180$^\circ$. D) 90$^\circ$. Show Answer Correct Answer: A) 0$^\circ$. 22. With the help of a phasor diagram, find the impedance of a series LCR circuit. A) Z = $\sqrt{R^2 + (X_L-X_C)^2}$. B) Z = $\sqrt{R^2 + X_L^2 + X_C^2}$. C) Z = R + (X L-X C). D) Z = $\sqrt{X_L^2 + X_C^2}$. Show Answer Correct Answer: A) Z = $\sqrt{R^2 + (X_L-X_C)^2}$. 23. The frequency of ac generator depends on A) Speed of rotation of coil. B) Amplitude of ac. C) Size of coil. D) All the above. Show Answer Correct Answer: A) Speed of rotation of coil. 24. What is the significance of phase difference in AC circuits? A) Phase difference only affects the frequency of the circuit. B) The significance of phase difference in AC circuits is to determine the power factor and efficiency of power transfer. C) Phase difference determines the color of the circuit components. D) Phase difference is irrelevant in resistive circuits. Show Answer Correct Answer: B) The significance of phase difference in AC circuits is to determine the power factor and efficiency of power transfer. 25. A pure capacitor is connected to an a.c. supply of frequency 50 Hz and r.m.s. voltage 6.0 V. If the r.m.s. value of the current in the circuit is 30 mA, what is the capacitance of the capacitor? A) 14 $\mu$. B) 13 $\mu$. C) 16 $\mu$. D) 15 $\mu$. Show Answer Correct Answer: C) 16 $\mu$. 26. What is the typical voltage of a single-phase AC supply in Great Britain? A) 110 V. B) 600 V. C) 400 V. D) 230 V. Show Answer Correct Answer: D) 230 V. 27. What is the main hazard associated with AC electricity in homes? A) Overheating. B) Electric shock. C) Noise pollution. D) Rusting. Show Answer Correct Answer: B) Electric shock. 28. You notice that a circuit breaker keeps tripping when you use a certain appliance. What is the most likely reason? A) The appliance is not plugged in. B) The appliance is using DC power. C) The appliance is using too little current. D) The appliance is causing an overload or short circuit. Show Answer Correct Answer: D) The appliance is causing an overload or short circuit. 29. The number of turns in a long solenoid is doubled; how does the inductance of the solenoid change? A) It is cut to a quarter. B) It doubles. C) It doesn't change. D) It quadruples. E) It is cut to a half. Show Answer Correct Answer: D) It quadruples. 30. Which of the following is a use of AC in homes? A) Running washing machines. B) Powering LED flashlights. C) Charging car batteries. D) Operating calculators. Show Answer Correct Answer: A) Running washing machines. 31. Power factor is maximum in an LCR series circuit when A) X$_{L}$=X$_{C}$. B) X$_{C}$ =0. C) X$_{L}$ =0. D) R=0. Show Answer Correct Answer: A) X$_{L}$=X$_{C}$. 32. What is the impedance in an AC circuit and how is it calculated? A) Impedance is calculated as Z = R-jX. B) Impedance is the total power consumed in a circuit. C) Impedance is only the resistance in a circuit. D) Impedance (Z) is calculated as Z = R + jX, where R is resistance and X is reactance. Show Answer Correct Answer: D) Impedance (Z) is calculated as Z = R + jX, where R is resistance and X is reactance. 33. Two advantages of AC over DC are: A) Easy to generate, easy to change voltage and current values. B) A comes before D in the alphabet. C) Don't know because I did not study this. D) None of the above. Show Answer Correct Answer: A) Easy to generate, easy to change voltage and current values. 34. What is the primary disadvantage of A.C.? A) More complex circuitry. B) Lower efficiency. C) Higher danger level. D) Higher cost. Show Answer Correct Answer: C) Higher danger level. 35. What is the SI unit for capacitive reactance? A) Ohm. B) Mho. C) Farad. D) Cordel. Show Answer Correct Answer: A) Ohm. 36. The Phase angle between Current and Voltage in a LCR circuit is given by A) Tan (XL-XC/R). B) Arctan (XC-XL/R). C) Arctan (XL-XC / R). D) Tan (XC-XL/R). Show Answer Correct Answer: B) Arctan (XC-XL/R). 37. What is the effect of placing a capacitor in parallel with a resistive load? A) It increases the frequency. B) It smooths the rectified voltage. C) It increases the resistance. D) It decreases the voltage. Show Answer Correct Answer: B) It smooths the rectified voltage. 38. Find the power suppled by the electric plant, if the power loss is negligible A) 1400 kW. B) 600 kW. C) 1600 kW. D) 500 kW. Show Answer Correct Answer: A) 1400 kW. 39. What are the primary applications of transformers? A) Thermal regulation, mechanical support, and fluid dynamics. B) Power generation, energy storage, and signal amplification. C) Data compression, error detection, and frequency modulation. D) Voltage transformation, circuit isolation, impedance matching, and signal processing. Show Answer Correct Answer: D) Voltage transformation, circuit isolation, impedance matching, and signal processing. 40. The circuit in which current and voltage are in phase, the power factor is: A) One. B) Two. C) Zero. D) Three. Show Answer Correct Answer: A) One. 41. If the frequency of the generator is increased, what happens to the output voltage? A) It decreases. B) It remains constant. C) It increases. D) It becomes zero. Show Answer Correct Answer: C) It increases. 42. A resistor, capacitor and inductor is connected in series with resistance of R = 400 $\Omega$, inductive reactance of X$_{L}$ = 500 $\Omega$ dan impedance of Z = 500 $\Omega$. Calculate the value of capacitive reactance from the capcitor. A) 400 $\Omega$. B) 300 $\Omega$. C) 200 $\Omega$. D) 500 $\Omega$. Show Answer Correct Answer: C) 200 $\Omega$. 43. How does a circuit breaker improve safety in AC household circuits? A) By increasing voltage. B) By automatically cutting off power during faults. C) By storing excess energy. D) By converting AC to DC. Show Answer Correct Answer: B) By automatically cutting off power during faults. 44. The graph of alternating current or alternating voltage is a ..... form. A) Square. B) Sawtooth. C) Triangle. D) Sinusoidal. Show Answer Correct Answer: D) Sinusoidal. 45. What is the effect of increasing frequency on capacitive reactance (XC)? A) XC decreases. B) XC becomes zero. C) XC increases. D) XC remains constant. Show Answer Correct Answer: A) XC decreases. 46. The self-induced voltage across an inductance is produced by a change in ..... A) Current with respect to time. B) Resistance with respect to time. C) Capacitance with respect to time. D) Voltage with respect to time. Show Answer Correct Answer: A) Current with respect to time. 47. In AC generator, emf changes sinusoidally because of: A) Variable magnetic field. B) Uniform rotation of coil. C) Constant flux. D) Linear motion of coil. Show Answer Correct Answer: B) Uniform rotation of coil. 48. The efficiency of power in an AC circuit is expressed by what term? A) True power. B) Apparent Power. C) Power factor. D) None of the above. Show Answer Correct Answer: C) Power factor. 49. Which of the following is a common source of alternating current (AC) in homes? A) Solar cell. B) Capacitor. C) Battery. D) Power plant. Show Answer Correct Answer: D) Power plant. 50. What is the total opposition to AC in a circuit containing resistors, inductors, and capacitors? A) Resistance. B) Conductance. C) Impedance. D) Reactance. Show Answer Correct Answer: C) Impedance. 51. An AC voltage is applied to a resistance R and an inductor L in series. If R and the inductive reactance are both equal to 3 $\Omega$ A) Zero. B) $\frac{\pi}{4}$. C) $\frac{\pi}{6}$. D) $\frac{\pi}{2}$. Show Answer Correct Answer: B) $\frac{\pi}{4}$. 52. What is one complete sequence of voltage or current changes from zero to a positive peak to zero, then through a negative peak and back to zero? A) Cycle. B) A bunch of electrical terms I don't know. C) Who cares?. D) None of the above. Show Answer Correct Answer: A) Cycle. 53. Which device provides direct current? A) Light bulb. B) Battery. C) Power plant. D) Outlet. Show Answer Correct Answer: B) Battery. 54. A current which periodically changes direction and magnitude is known as A) Direct Current. B) Alternating Current. C) Pulsating DC. D) None of the above. Show Answer Correct Answer: B) Alternating Current. 55. What does a Band Pass filter do? A) Blocks low frequency signals. B) Blocks high frequency signals. C) Allows a specific range of signals. D) Blocks a specific range of signals. Show Answer Correct Answer: C) Allows a specific range of signals. 56. Which type of current is used in mains electricity A) Alternating Current (AC). B) Direct Current (DC). C) All the above. D) None of the above. Show Answer Correct Answer: A) Alternating Current (AC). 57. What does the Root Mean Square (RMS) value represent in AC? A) The peak value of current. B) The instantaneous value of AC. C) The effective value of AC. D) The average value of current. Show Answer Correct Answer: C) The effective value of AC. 58. Which of the following is true about an inductor? I. It stores energy after the current stops flowing II. It opposes the change of current III. It can produce a magnetic field A) I. B) III. C) I and II. D) II and III. E) All of the above. Show Answer Correct Answer: D) II and III. 59. What type of electricity is used in our houses? A) Direct Currents. B) Alternating Currents. C) All the above. D) None of the above. Show Answer Correct Answer: B) Alternating Currents. 60. A 120 volt ac source is connected across a pure inductor of inductance 0.70 henry. If the frequency of the source is 60 Hz, the current passing through the inductor is ..... A) 0.455 amps. B) 0.355 amps. C) 4.55 amps. D) 3.55 amps. Show Answer Correct Answer: A) 0.455 amps. ← 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 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 9 🏠 Back to Homepage 📘 Download PDF Books 📕 Premium PDF Books