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 12 🏠 Homepage 📘 Download PDF Books 📕 Premium PDF Books Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 12 (60 MCQs) Quiz Instructions Select an option to see the correct answer instantly. 1. What is the main difference between alternating current (a.c.) and direct current (d.c.)? A) C. flows in one direction only. B) C. changes direction periodically. C) C. changes direction periodically. D) C. flows in both directions. Show Answer Correct Answer: B) C. changes direction periodically. 2. An LCR series circuit, connected to a source $\epsilon$ A) The voltage across R equals applied voltage. B) The voltage across C equals applied voltage. C) The voltage across C is zero. D) The voltage across R is zero. Show Answer Correct Answer: A) The voltage across R equals applied voltage. 3. Inductive reactance increases as the ..... A) Impedance increases. B) Frequency increases. C) Frequency decreases. D) Impedance decreases. Show Answer Correct Answer: B) Frequency increases. 4. The r.m.s value of an alternating current is given by steady (D.C) current which when flowing through a given circuit for a given time produces A) The more heat than produced by A.C when flowing through the sam circuit. B) The less heat than produced by A.C when flowing through the sam circuit. C) The same heat than produced by A.C when flowing through the same circuit. D) None of the above. Show Answer Correct Answer: C) The same heat than produced by A.C when flowing through the same circuit. 5. The number of instantaneous values between zero and the peak value is A) One. B) Eleven. C) Infinity. D) Zero. Show Answer Correct Answer: C) Infinity. 6. In general, in an alternating circuit A) The average value of current is zero. B) The average value of the square of the current is zero. C) The average power dissipation is zero. D) The phase difference between current and voltage is zero. Show Answer Correct Answer: A) The average value of current is zero. 7. A pure inductor of inductance 0.20 H and a resistor of resistance 200 $\Omega$ A) 10 A. B) 1.1 A. C) 9.3 A. D) 8.8 A. Show Answer Correct Answer: B) 1.1 A. 8. What is the main difference between single-phase and three-phase waveforms? A) Single-phase has one waveform, three-phase has three waveforms. B) Single-phase has three wires, three-phase has one wire. C) Single-phase is more efficient than three-phase. D) Single-phase is used for industrial purposes, three-phase is for residential. Show Answer Correct Answer: A) Single-phase has one waveform, three-phase has three waveforms. 9. At higher frequencies, which of the following plays a dominant role in RLC series circuit A) Resistor. B) Capacitor. C) Inductor. D) Transistor. Show Answer Correct Answer: C) Inductor. 10. What is the frequency of an AC waveform that completes 20 cycles per half second? A) 10Hz. B) 40Hz. C) 30Hz. D) 20Hz. Show Answer Correct Answer: B) 40Hz. 11. At resonance, find the value of current A) 22.52 A. B) 14.14 A. C) 47.41 A. D) 50.25 A. Show Answer Correct Answer: B) 14.14 A. 12. An electric current always produces ..... A) Mutual inductance. B) A magnetic field. C) Capacitive reactance. D) High voltage. Show Answer Correct Answer: B) A magnetic field. 13. A series circuit consists of R = 20 $\Omega$, L = 20 mH, and AC supply 60 V with f = 100 Hz. The voltage drop across L is A) 31.9 V. B) 45.5 V. C) 50.5 V. D) 39.1 V. Show Answer Correct Answer: A) 31.9 V. 14. $\frac{10\angle-10}{5\angle30}$ A) $2\angle-40$. B) $5\angle20$. C) All the above. D) None of the above. Show Answer Correct Answer: A) $2\angle-40$. 15. A student observes that the lights in their house flicker when a large appliance is turned on. What could be the reason? A) The appliance is drawing a large amount of AC current, causing voltage fluctuations. B) The lights are faulty. C) The appliance is using DC power. D) The house wiring is made of plastic. Show Answer Correct Answer: A) The appliance is drawing a large amount of AC current, causing voltage fluctuations. 16. The frequency of direct current (DC) is: A) 60 Hz. B) 100 Hz. C) 0 Hz. D) 50 Hz. Show Answer Correct Answer: C) 0 Hz. 17. The distance that a signal's energy can travel in the time it takes for one cycle to occur is called the signal's: A) Wavelength. B) Period. C) Frequency. D) Amplitude. Show Answer Correct Answer: A) Wavelength. 18. In an AC circuit, if the voltage is given by v=5.0 sin(628t), what is the peak voltage? A) 0 V. B) 5.0 V. C) 10 V. D) 2.5 V. Show Answer Correct Answer: B) 5.0 V. 19. What does the Q-factor measure in a circuit? A) Sharpness of resonance. B) Voltage. C) Power. D) Current. Show Answer Correct Answer: A) Sharpness of resonance. 20. What is the formula for calculation capacitive reactance? A) $X_C=\frac{1}{2\pi fC}$. B) $X_C=2\pi fC$. C) $X_L=2\pi fL$. D) None of the above. Show Answer Correct Answer: A) $X_C=\frac{1}{2\pi fC}$. 21. The variation of a quantity such as voltage or current shown on a graph is known as ..... A) Period. B) Peak value. C) Instantaneous value. D) Waveform. Show Answer Correct Answer: D) Waveform. 22. In radio Circuit, a capacitor of 2microfarad is used, if the frequency is 1000Hz and current flowing in it is 1mA, then Calculate the Voltage across the capacitor A) 29.57mV. B) 59.57mV. C) 39.57mV. D) 79.57mV. Show Answer Correct Answer: D) 79.57mV. 23. RMS value of AC is numerically: A) Independent of peak value. B) Less than peak value. C) Greater than peak value. D) Equal to peak value. Show Answer Correct Answer: B) Less than peak value. 24. The period of a wave is A) The same as frequency. B) Time required to complete one cycle. C) Expressed in amperes. D) None of the above. Show Answer Correct Answer: B) Time required to complete one cycle. 25. The power factor can be defined as the ratio of true power to ..... A) Apparent power. B) Reactive power. C) Total current. D) Total resistance. Show Answer Correct Answer: A) Apparent power. 26. What happens to the current at resonance in an L-C circuit? A) It is zero. B) It is minimum. C) It is maximum. D) It is constant. Show Answer Correct Answer: C) It is maximum. 27. If frequency of rotating coil of an A.C. generator is f Hz then frequency of e.m.f. produced in Pakistan is: A) 50 Hz. B) 60 Hz. C) F Hz. D) None of these. Show Answer Correct Answer: C) F Hz. 28. What is the main source of alternating current for homes? A) Solar cells. B) Batteries. C) Power plants. D) Fuel cells. Show Answer Correct Answer: C) Power plants. 29. A wire carries an alternating current of peak value 3 A. Which of the following is the root-mean-square value of this current? A) 2.1 A. B) 4.2 A. C) 9.0 A. D) 1.5 A. Show Answer Correct Answer: A) 2.1 A. 30. Which of the following is NOT a component of a simple single-phase AC generator? A) Rotor. B) Stator. C) Transformer. D) Slip rings. Show Answer Correct Answer: C) Transformer. 31. If the circuit is at resonance the impedance becomes A) Ohmic resistance. B) Maximum. C) Minimum. D) Capacitive or inductive reactance. Show Answer Correct Answer: A) Ohmic resistance. 32. A transformer steps up 220 V to 2200 V. What is the transformation ratio? A) 0.1. B) 10. C) 0.2. D) 20. Show Answer Correct Answer: B) 10. 33. The following statement describe about an capacitance except ..... A) Ability to store charge for a given amount of voltage supply. B) Represented by C. C) Standard unit is Farad. D) Voltage is always leading current. Show Answer Correct Answer: D) Voltage is always leading current. 34. The number of cycles a waveform completes per second determines the ..... A) Resistance. B) Frequency. C) Amperage. D) Voltage. Show Answer Correct Answer: B) Frequency. 35. When a conductor cuts the magnetic flux lines at?, the maximum voltage will be induced into the conductor. A) 360 deg. B) 60 deg. C) 90 deg. D) 180 deg. Show Answer Correct Answer: C) 90 deg. 36. Which component is commonly found in AC circuits to store electrical energy? A) Capacitor. B) Diode. C) Resistor. D) Transistor. Show Answer Correct Answer: A) Capacitor. 37. What is one-half of an AC cycle? A) Alternation. B) Altercation. C) Don't know because I did not study this. D) None of the above. Show Answer Correct Answer: A) Alternation. 38. Capacitors are sometimes used in DC circuits to A) Counteract inductive reactance at specific locations. B) Smooth out slight pulsations in current/voltage. C) Assist in stepping voltage and current up and/or down. D) None of the above. Show Answer Correct Answer: B) Smooth out slight pulsations in current/voltage. 39. A student is asked to explain why transformers are used in AC power transmission but not in DC transmission. What is the correct explanation? A) Transformers work only with DC because DC changes direction. B) Transformers require alternating current to operate, as they rely on changing magnetic fields. C) Transformers can operate with both AC and DC. D) Transformers are used to store energy. Show Answer Correct Answer: B) Transformers require alternating current to operate, as they rely on changing magnetic fields. 40. Which of the following instrument may be used to measure AC A) Voltmeter. B) Moving coil galvanometer. C) Hot wire meters. D) Ballistic galvanometer. Show Answer Correct Answer: C) Hot wire meters. 41. A device that uses electromagnetic induction to transfer electrical energy from one circuit to another is a(n) ..... A) Transformer. B) Coil. C) Inductor. D) Capacitor. Show Answer Correct Answer: A) Transformer. 42. Fill in the blank:Hair growth will take longer to ..... A) Re-grow. B) Fall. C) Change. D) Stop. Show Answer Correct Answer: A) Re-grow. 43. The voltage of domestic AC is 220 V. What does this represent? A) Root mean square voltage. B) Peak voltage. C) Root mean voltage. D) Mean voltage. Show Answer Correct Answer: A) Root mean square voltage. 44. How can phase difference be represented graphically? A) Phase difference can be represented graphically by plotting waveforms and observing the horizontal shift between them. B) Through the frequency of the waves. C) By calculating the wavelength of the waves. D) By measuring the amplitude of the waves. Show Answer Correct Answer: A) Phase difference can be represented graphically by plotting waveforms and observing the horizontal shift between them. 45. The distance of the waveform travel in one cycle is referred to A) Wavelength. B) Amplitude. C) Time. D) Frequency. Show Answer Correct Answer: A) Wavelength. 46. The Analog of resistance in a purely inductive circuit is called A) Inductive Resistance. B) Admittance. C) Inductive Reactance. D) Impedance. Show Answer Correct Answer: C) Inductive Reactance. 47. The time required for one cycle of events to occur is known as A) Period. B) Headache. C) Mind-numbing. D) None of the above. Show Answer Correct Answer: A) Period. 48. The phase difference between voltage and current in a purely inductive circuit A) 180. B) -90. C) 90. D) 0. Show Answer Correct Answer: B) -90. 49. If the current in an inductor is tripled, by what factor does the stored energy change? A) 1/9. B) 4.5. C) 9. D) 2. Show Answer Correct Answer: C) 9. 50. A dry-cell battery produces ..... A) An alternating current. B) A direct current. C) Both direct and alternating current. D) The same current that a generator produces. Show Answer Correct Answer: B) A direct current. 51. In a pure capacitor ac circuit A) Current lead voltage by 90'. B) Voltage lead current by 90'. C) Both current and voltage are in phase. D) Current and voltage are out of phase. Show Answer Correct Answer: A) Current lead voltage by 90'. 52. What is a common method used to reduce energy losses in AC power lines? A) Using superconducting materials. B) Increasing the frequency of the AC. C) Converting AC to DC. D) Transmitting at high voltages. Show Answer Correct Answer: D) Transmitting at high voltages. 53. The RMS value of an AC Wave is the A) Effective DC Value. B) Average value. C) Some made up value. D) None of the above. Show Answer Correct Answer: A) Effective DC Value. 54. How does voltage affect electrical currents? A) If the voltage in the object increases the current will increase. B) If the voltage in the object increases the current will decrease. C) The voltage of an object has no effect on the current. D) If the voltage in the object decreases the current will increase. Show Answer Correct Answer: A) If the voltage in the object increases the current will increase. 55. Find the maximum power dissipated in the circuit A) 4700 W. B) 2200 W. C) 2299.3 W. D) 5500 W. Show Answer Correct Answer: C) 2299.3 W. 56. Explain the concept of frequency in AC circuits. A) Frequency is the resistance in an AC circuit. B) Frequency is the voltage level in an AC circuit. C) Frequency is the amount of current flowing in an AC circuit. D) Frequency is the number of cycles per second in an AC circuit, measured in hertz (Hz). Show Answer Correct Answer: D) Frequency is the number of cycles per second in an AC circuit, measured in hertz (Hz). 57. What type of current is typically used in electronic devices? A) Direct current B) Alternating current C) Both A and B D) None of the above A) Static current. B) Pulsating current. C) A) Direct current. D) High frequency current. Show Answer Correct Answer: C) A) Direct current. 58. A coil intercepts a magnetic flux of 0.2 x 10$^{-2}$ Wb in 0.1s. What is the emf induced in the coil? A) 2V. B) 0.2V. C) 0.002V. D) 0.02V. Show Answer Correct Answer: D) 0.02V. 59. The combine opposition of resistor, capacitor and inductor is called A) Reactance. B) Resistor. C) Impedance. D) None. Show Answer Correct Answer: C) Impedance. 60. How does RMS voltage differ from average voltage? A) RMS voltage is higher than average voltage for AC signals, as it represents the effective value. B) RMS voltage and average voltage are identical for all waveforms. C) RMS voltage is always lower than average voltage. D) Average voltage is used exclusively for DC signals. Show Answer Correct Answer: A) RMS voltage is higher than average voltage for AC signals, as it represents the effective value. ← 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