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 15 🏠 Homepage 📘 Download PDF Books 📕 Premium PDF Books Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 15 (60 MCQs) Quiz Instructions Select an option to see the correct answer instantly. 1. When A.C. pass through an inductor, voltage leads the current by: A) Half cycle. B) Quarter cycle. C) Full cycle. D) None of these. Show Answer Correct Answer: B) Quarter cycle. 2. Root Mean Square Value means A) The Average of root of square of a quantity. B) $\sqrt{2}$. C) The root of average of square of a quantity. D) The root of Square of Average of a quantity. Show Answer Correct Answer: C) The root of average of square of a quantity. 3. An alternating current with 200 V voltage and 25 Hz frequency is flowing through a 200 $\Omega$ resistor and $\frac{100}{\pi}\mu F$ A) -$\frac{1}{2}\sqrt{2}$. B) $\frac{1}{2}\sqrt{3}$. C) $\frac{1}{2}\sqrt{2}$. D) $\frac{1}{4}\sqrt{3}$. E) $\frac{1}{2}$. Show Answer Correct Answer: C) $\frac{1}{2}\sqrt{2}$. 4. Basic Electrical system consists of: A) Source, voltage, load. B) Source, switch, conductor. C) Source, conductor, load. D) Switch, fuse, load. Show Answer Correct Answer: C) Source, conductor, load. 5. The relationship between the capacitive reactance of a capacitor is A) Directly proportional to the frequency of the AC source. B) Inversely proportional to the frequency of the AC source. C) Directly proportional to the capacitance of the capacitor. D) None of the above. Show Answer Correct Answer: B) Inversely proportional to the frequency of the AC source. 6. An alternating current of rms value 10 A is passed through a 12 $\Omega$ A) 20 V. B) 90 V. C) 169.7 V. D) None of these. Show Answer Correct Answer: C) 169.7 V. 7. The total capacitance of two 5$\mu$F capacitors and one 10$\mu$F capacitor connected in parallel is ..... A) 25$\mu$F. B) 15$\mu$F. C) 5$\mu$F. D) 20$\mu$F. Show Answer Correct Answer: D) 20$\mu$F. 8. A Capacitor blocks A) Only a.c. B) Only d.c. C) Both ac and dc. D) None of these. Show Answer Correct Answer: B) Only d.c. 9. Many household appliances are connected to a 230 V rms mains supply. What is the peak voltage of a household's mains supply? A) 325 V. B) 230 V. C) 0 V. D) 115 V. Show Answer Correct Answer: A) 325 V. 10. Which of the following are uses of short wave diathermy? A) Suitable for fine and coarse hair growth. B) Suitable for use with flash technique. C) Both A and B. D) None of the above. Show Answer Correct Answer: C) Both A and B. 11. Which of the following is a safety precaution when working with AC electricity? A) Use wet hands. B) Wear rubber gloves. C) Stand on metal surface. D) Ignore warning signs. Show Answer Correct Answer: B) Wear rubber gloves. 12. At the resonant frequency, impedance(Z) equals what? A) $X_L$. B) $R$. C) $X_C$. D) $R^2+\left(X_L-X_C\right)^2$. Show Answer Correct Answer: B) $R$. 13. Which of the following equations represent ac current A) $I=I_o\cos\left(\omega t\right)$. B) $I=I_o\sin\left(2\pi ft\right)$. C) $I=I_o\cos\left(t\right)$. D) $I=I_o\sin\left(\frac{2\pi}{f}t\right)$. Show Answer Correct Answer: B) $I=I_o\sin\left(2\pi ft\right)$. 14. Which of the following waves are produced by moving electric and magnetic fields? A) Electromagnetic. B) Magnetic. C) Ultra magnetic. D) Electronic. Show Answer Correct Answer: A) Electromagnetic. 15. The cause of induced e.m.f. in a closed coil is A) Magnetic field. B) Magnetic flux. C) Change in magnetic flux. D) None of these. Show Answer Correct Answer: C) Change in magnetic flux. 16. Satuan dari Impedansi (Z) adalah Ohm A) BENAR. B) SALAH. C) All the above. D) None of the above. Show Answer Correct Answer: A) BENAR. 17. The impedance of a circuit consists of 3 ohm resistance and 4 ohm reactance. The power factor of the circuit is ..... A) 0.8. B) 0.4. C) 1.0. D) 0.6. Show Answer Correct Answer: D) 0.6. 18. What is the opposition to AC by an inductor called? A) Impedance. B) Inductive Reactance. C) Resistance. D) Capacitive Reactance. Show Answer Correct Answer: B) Inductive Reactance. 19. A pure capacitor is connected to an AC power supply. In this circuit, the current A) Leads the voltage by 90$^\circ$. B) Lags the voltage by 90$^\circ$. C) Is in phase with the voltage. D) None of the given answers. Show Answer Correct Answer: A) Leads the voltage by 90$^\circ$. 20. In an inductive AC circuit, when the applied voltage is at its maximum negative value, the current is ..... A) At the maximum positive value. B) Zero. C) At the maximum negative value. D) Increasing toward maximum positive. Show Answer Correct Answer: B) Zero. 21. What is the term for the overall resistance in an RLC circuit? A) Impedance. B) Reactance. C) Voltage. D) Current. Show Answer Correct Answer: A) Impedance. 22. What is produced when the conductor crosses the lines of force at 90$^\circ$? A) Constant voltage. B) Maximum positive emf. C) No emf. D) Maximum negative emf. Show Answer Correct Answer: B) Maximum positive emf. 23. For a given AC source, maximum average power is dissipated when circuit is: A) Open. B) Resonant. C) Purely inductive. D) Purely capacitive. Show Answer Correct Answer: B) Resonant. 24. The frequency of DC in our country is A) 50 cycles/s. B) 30 cycles/s. C) 60 cycles/s. D) 0 cycles/s. Show Answer Correct Answer: D) 0 cycles/s. 25. What is the effect of the speed of the conductor on the generation of emf? A) It only affects the frequency. B) It has no effect. C) It increases the emf. D) It decreases the emf. Show Answer Correct Answer: C) It increases the emf. 26. A bulb is connected with an AC source through an inductor.How the glow of the bulb will be affected if an iron rod is inserted in the core of the inductor A) It will decrease. B) The bulb will stop glowing. C) Remain same. D) It will increase. Show Answer Correct Answer: A) It will decrease. 27. A bike-dynamo is rotated by hand, with its terminals attached to the inputs of a CRO. If it is rotated twice as fast, A) The amplitude and frequency of the voltage will both double. B) The amplitude will double and the frequency will be unchanged. C) The amplitude will be unchanged and the frequency will double. D) The amplitude will increase by four times and the frequency will double. Show Answer Correct Answer: A) The amplitude and frequency of the voltage will both double. 28. Peak to Peak voltage is A) Vmax-0. B) Vmax-Vmin. C) Tmax-tmin. D) Tmax-Tmin. Show Answer Correct Answer: B) Vmax-Vmin. 29. A series RLC circuit has a resistance of 10.0 $\Omega$ and a impedance of 50.0 $\Omega$. If the rms voltage applied to the circuit is 10 V, what average power? A) 0.4W. B) 5W. C) 50W. D) 4W. Show Answer Correct Answer: A) 0.4W. 30. A series RLC circuit is connected across a 240V, 50 Hz supply. When the voltage across capacitor is 250V, a maximum current of 0.5A flows in the circuit. Find the resistance. A) 1000 Ohms. B) 480 Ohms. C) 100 Ohms. D) 500 Ohms. Show Answer Correct Answer: B) 480 Ohms. 31. What is a primary advantage of AC over DC in terms of infrastructure? A) AC infrastructure is more prone to weather damage. B) AC infrastructure is more expensive to build. C) AC requires less complex infrastructure for voltage transformation. D) AC infrastructure requires more frequent maintenance. Show Answer Correct Answer: C) AC requires less complex infrastructure for voltage transformation. 32. How do you determine the total impedance in a parallel circuit? A) Z total = 1 / (1/Z1 + 1/Z2 + + 1/Zn). B) Z total = max(Z1, Z2, , Zn). C) Z total = Z1 + Z2 + + Zn. D) Z total = Z1 * Z2 / (Z1 + Z2). Show Answer Correct Answer: A) Z total = 1 / (1/Z1 + 1/Z2 + + 1/Zn). 33. What happens to the impedance of a series RLC circuit when the frequency is increased beyond the resonant frequency? A) It decreases. B) It increases. C) It remains constant. D) It becomes zero. Show Answer Correct Answer: B) It increases. 34. The value of an alternating quantity at a particular instant of time in a cycle is A) Instantaneous value. B) Frequency. C) All the above. D) None of the above. Show Answer Correct Answer: A) Instantaneous value. 35. What is the relationship between inductive reactance and capacitive reactance at resonance? A) Inductive reactance is always greater than capacitive reactance. B) Capacitive reactance equals zero at resonance. C) Inductive reactance and capacitive reactance are unrelated at resonance. D) Inductive reactance equals capacitive reactance at resonance. Show Answer Correct Answer: D) Inductive reactance equals capacitive reactance at resonance. 36. $2\angle25\times4\angle-10$ A) $8\angle15$. B) $6\angle15$. C) $8\angle35$. D) $8\angle250$. Show Answer Correct Answer: A) $8\angle15$. 37. If the frequency of ac is made 4 times of its initial value, the inductive reactance will A) Remain the same. B) Be 2 times. C) Be 4 times. D) Be half. Show Answer Correct Answer: C) Be 4 times. 38. Explain the concept of apparent power in AC circuits. A) Apparent power is the power consumed by resistors in a circuit. B) Apparent power is measured in watts (W) and represents only reactive power. C) Apparent power is only the real power in an AC circuit. D) Apparent power is the total power in an AC circuit, measured in volt-amperes (VA), combining real and reactive power. Show Answer Correct Answer: D) Apparent power is the total power in an AC circuit, measured in volt-amperes (VA), combining real and reactive power. 39. In a three-phase AC generator, how many degrees apart are the phases? A) 90 degrees. B) 120 degrees. C) 180 degrees. D) 60 degrees. Show Answer Correct Answer: B) 120 degrees. 40. Modified from CIE J81/II/19. An alternating current of r.m.s. magnitude 3.0 A and a steady direct current I flowing through identical resistors dissipate heat at equal rates.What is the value of current I? A) 1.5 A. B) 3.0 A. C) 2.1 A. D) 4.2 A. Show Answer Correct Answer: B) 3.0 A. 41. State whether the following statement is TRUE or FALSE; Electromagnetic waves can travel through a vacuum. A) TRUE. B) FALSE. C) All the above. D) None of the above. Show Answer Correct Answer: A) TRUE. 42. The main reason that alternating current replaced direct current for general use is: A) Electric clocks do not work on dc. B) Ac generators do not need slip rings. C) Ac voltages may be conveniently transformed. D) A given ac current does not heat a power line as much as the same dc current. Show Answer Correct Answer: C) Ac voltages may be conveniently transformed. 43. What is the main reason AC is used in the national grid? A) AC is cheaper to produce. B) AC can be easily transformed to different voltage levels for efficient transmission. C) AC is more reliable than DC. D) AC is less affected by power surges. Show Answer Correct Answer: B) AC can be easily transformed to different voltage levels for efficient transmission. 44. Why is AC preferred over DC for long-distance power transmission? A) AC is more environmentally friendly. B) AC can be transmitted at higher voltages, reducing energy losses. C) AC is easier to generate. D) AC is safer for wildlife. Show Answer Correct Answer: B) AC can be transmitted at higher voltages, reducing energy losses. 45. Phasors normally A) Do not have a direction. B) Rotate anti-clockwise. C) Rotate clockwise. D) Do not represent real values. Show Answer Correct Answer: B) Rotate anti-clockwise. 46. In which of the following circuits, the power average can be zero? A) Purely inductive circuit. B) LCR circuit. C) Both LC and LCR circuit. D) None of the above. Show Answer Correct Answer: A) Purely inductive circuit. 47. The frequency of A.C. mains in India is A) 120 c/s. B) 50 c/s. C) 60 c/s. D) 30 c/s. Show Answer Correct Answer: B) 50 c/s. 48. What is the effect of skin effect in A.C. circuits? A) No effect. B) Increased capacitance. C) Decreased resistance. D) Increased resistance. Show Answer Correct Answer: D) Increased resistance. 49. The waveform of alternating current produced by a rotating generator is called a A) Sine wave. B) Big wave. C) Don't care because I hate this class. D) None of the above. Show Answer Correct Answer: A) Sine wave. 50. What type of connection is used in a three-phase AC circuit? A) Series connection. B) Parallel connection. C) Star and delta connections. D) Single connection. Show Answer Correct Answer: C) Star and delta connections. 51. Which best defines the meaning of the r.m.s. value of a sinusoidal alternating current? A) Steady current that delivers more power to a resistive load than the mean power of the a.c. B) Alternating current that delivers the same mean power to a resistive load as the d.c. C) Alternating current that delivers more power to a resistive load as the mean power of the d.c. D) Steady current that delivers the same power to a resistive load as mean power of the a.c. Show Answer Correct Answer: D) Steady current that delivers the same power to a resistive load as mean power of the a.c. 52. Eddy currents in the core of transformer can't be developed by A) Increasing the number of turns in secondary coil. B) Using a weak ac at high potential. C) Taking laminated transformer. D) Making step down transformer. Show Answer Correct Answer: C) Taking laminated transformer. 53. Quantity that remains unchanged in a transformer is A) Voltage. B) Current. C) Frequency. D) None of these. Show Answer Correct Answer: C) Frequency. 54. State whether the following statements is TRUE or FALSE;The electric field in an electromagnetic wave is non-oscillating. A) True. B) False. C) All the above. D) None of the above. Show Answer Correct Answer: A) True. 55. The power dissipated in the primary coil is A) 6 W. B) 0.24 W. C) 12 W. D) 24 W. Show Answer Correct Answer: B) 0.24 W. 56. If the inductance of an inductor is halved, how does its inductive reactance change at a constant frequency? A) It halves. B) It remains the same. C) It doubles. D) It quadruples. Show Answer Correct Answer: A) It halves. 57. What is one of the main advantages of alternating current (AC) over direct current (DC) in power transmission? A) AC can be easily stored in batteries. B) AC can be transmitted over long distances with lower energy losses. C) AC is safer than DC for all applications. D) AC is cheaper to produce than DC. Show Answer Correct Answer: B) AC can be transmitted over long distances with lower energy losses. 58. Each of three equal capacitors in series has ..... A) The original value of the applied voltage. B) Three times the applied voltage. C) One-third the applied voltage. D) Twice the applied voltage. Show Answer Correct Answer: C) One-third the applied voltage. 59. What does resonant frequency mean? A) The frequency at which the capacitive reactance and inductive reactance cancel out. B) The frequency at which capacitance and inductance are equal. C) The frequency at which a sine wave appears more like a straight line. D) None of the above. Show Answer Correct Answer: A) The frequency at which the capacitive reactance and inductive reactance cancel out. 60. A bulb of resistance 10 Ohm and a capacitor of capacitance 800 uF are connected in series to a source of alternating voltage V = 200 sin 300t. Calculate the impedance of the circuit A) 4.17 Ohm. B) 18.5 Ohm. C) 10.8 Ohm. D) 10.0 Ohm. Show Answer Correct Answer: C) 10.8 Ohm. ← 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 7Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 8 🏠 Back to Homepage 📘 Download PDF Books 📕 Premium PDF Books