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 8 🏠 Homepage 📘 Download PDF Books 📕 Premium PDF Books Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 8 (60 MCQs) Quiz Instructions Select an option to see the correct answer instantly. 1. Diodes are used in electrical power supply circuits primarily as A) Switches. B) Rectifiers. C) Relays. D) None of the above. Show Answer Correct Answer: B) Rectifiers. 2. If the frequency of the AC voltage across an inductor is doubled, the inductive reactance of that inductor A) Decreases to one-half its original value. B) Increases to 4 times its original value. C) Decreases to one-fourth its original value. D) Increases to twice its original value. Show Answer Correct Answer: D) Increases to twice its original value. 3. . For unity power factor the circuit should be A) Purely capacitive. B) Purely resistive. C) LCR series circuit. D) Purely inductive. Show Answer Correct Answer: B) Purely resistive. 4. Peak to Peak voltage equals A) 2*Amplitude. B) 2*Vmax. C) 2*Vp. D) All of the above. Show Answer Correct Answer: D) All of the above. 5. At resonance, which of the physical quantity(s) is/are maximum? A) Current. B) Impedance. C) Both a and b. D) None of these. Show Answer Correct Answer: A) Current. 6. What is the phase difference between voltage and current in an alternating current circuit if the inductive reactance is 26 Ohm, the capasitive reactance is 20 Ohm and the active resistance is 8 Ohm? A) 53$^{0}$. B) 120$^{0}$. C) 25$^{0}$. D) 67$^{0}$. Show Answer Correct Answer: A) 53$^{0}$. 7. As frequency of an ac circuit increases, the current first increases and then decreases. What combination of circuit elements is most likely to comprise the circuit? A) Inductor and capacitor. B) Resistor and inductor. C) Resistor and capacitor. D) Resistor, inductor and capacitor. Show Answer Correct Answer: A) Inductor and capacitor. 8. What type of current more efficiently provides energy further distances? A) Direct currents. B) Variable currents. C) Alternating currents. D) Pulsating currents. Show Answer Correct Answer: C) Alternating currents. 9. How does the power factor affect AC circuits? A) The power factor affects the efficiency and performance of AC circuits by indicating how effectively the electrical power is being converted into useful work. B) The power factor only affects DC circuits. C) A higher power factor always leads to higher voltage. D) The power factor has no impact on AC circuits. Show Answer Correct Answer: A) The power factor affects the efficiency and performance of AC circuits by indicating how effectively the electrical power is being converted into useful work. 10. Transformer works on the principle of A) Mutual induction. B) Converter. C) Inverter. D) Total internal reflection. Show Answer Correct Answer: A) Mutual induction. 11. Why is AC more efficient for power transmission over long distances compared to DC? A) AC requires less maintenance. B) AC can be transmitted at higher voltages, reducing current and energy losses. C) AC is less affected by weather conditions. D) AC cables are cheaper to manufacture. Show Answer Correct Answer: B) AC can be transmitted at higher voltages, reducing current and energy losses. 12. Explain the significance of power factor in AC circuits. A) Power factor in AC circuits is significant as it indicates how effectively electrical power is being converted into useful work. A higher power factor means more efficient power usage. B) Power factor is a measure of voltage stability. C) Power factor has no impact on electrical efficiency. D) Power factor only affects DC circuits. Show Answer Correct Answer: A) Power factor in AC circuits is significant as it indicates how effectively electrical power is being converted into useful work. A higher power factor means more efficient power usage. 13. What is the primary reason AC is used in household power supply? A) AC is cheaper to produce. B) AC can be easily transformed to the required voltage levels. C) AC is safer than DC. D) AC is more environmentally friendly. Show Answer Correct Answer: B) AC can be easily transformed to the required voltage levels. 14. A 100 turn coil of area 0.1m$^{2}$ rotates at half a revolution per second. It is placed in a magnetic field of 0.01T perpendicular to the axis of the coil. Calculate the maximum voltage generated in the coil. A) 31.4V. B) 3.14V. C) 314V. D) 0.314V. Show Answer Correct Answer: D) 0.314V. 15. The total capacitance of two 15$\mu$F capacitors connected in series is ..... A) 15$\mu$F. B) 7.5$\mu$F. C) 5$\mu$F. D) 30$\mu$F. Show Answer Correct Answer: B) 7.5$\mu$F. 16. How do you calculate the total impedance in a series AC circuit? A) Z = R * (XL + XC). B) Z = R-j(XL + XC). C) Z = R + j(XC-XL). D) Z = R + j(XL-XC). Show Answer Correct Answer: D) Z = R + j(XL-XC). 17. The formula for inductive reactance is A) $\omega L$. B) $\frac{1}{\omega C}$. C) $\frac{1}{\omega L}$. D) $\omega C$. Show Answer Correct Answer: A) $\omega L$. 18. Which of the following is a reason why AC is used in household wiring instead of DC? A) AC can be easily transformed to higher or lower voltages. B) DC is easier to generate. C) AC is less dangerous. D) DC is more efficient for appliances. Show Answer Correct Answer: A) AC can be easily transformed to higher or lower voltages. 19. In an RLC series circuit at resonance: A) Impedance is maximum. B) Current is maximum. C) Power factor is zero. D) Current is minimum. Show Answer Correct Answer: B) Current is maximum. 20. What device converts mechanical energy into electrical energy using alternating current? A) Battery. B) Transformer. C) Rectifier. D) AC Generator. Show Answer Correct Answer: D) AC Generator. 21. In a circuit that has both capacitance and resistance, the current will lead the voltage ..... A) Because the resistance is too small to have an effect on circuit operation. B) Because the voltage across the branches is the same. C) By some angle between 0$^\circ$ and 90$^\circ$. D) With an impedance between 0 and 1. Show Answer Correct Answer: C) By some angle between 0$^\circ$ and 90$^\circ$. 22. If two objects have unlike charges they will do this. A) Friction. B) Induction. C) Attract. D) Repel. Show Answer Correct Answer: C) Attract. 23. Describe the behavior of current in a capacitor when connected to an AC source. A) The current in a capacitor leads the voltage by 90 degrees when connected to an AC source. B) The current in a capacitor is constant regardless of frequency. C) The current in a capacitor lags the voltage by 90 degrees. D) The current and voltage are in phase in a capacitor. Show Answer Correct Answer: A) The current in a capacitor leads the voltage by 90 degrees when connected to an AC source. 24. What is a Direct Current? A) An electric current flowing in one direction only. B) An electrical current flowing in many directions. C) A current that is never a straight line. D) A current with a high frequency. Show Answer Correct Answer: A) An electric current flowing in one direction only. 25. In an LCR series AC circuit, if $\omega_o$ A) $\left(\frac{1}{R}\right)\sqrt{\frac{L}{C}}$. B) $\frac{\omega_oC}{R}$. C) $\frac{\omega_oL}{C}$. D) $\frac{L}{\omega_oR}$. Show Answer Correct Answer: A) $\left(\frac{1}{R}\right)\sqrt{\frac{L}{C}}$. 26. What is the time-averaged value of power in an AC circuit called? A) Reactive Power. B) Instantaneous Power. C) Average Power. D) Peak Power. Show Answer Correct Answer: C) Average Power. 27. The power factor is defined as A) Cosine of the phase difference between voltage and current. B) Ratio of resistance with impedance. C) Ratio of active power with apparent power. D) All of above. Show Answer Correct Answer: D) All of above. 28. What is the role of capacitors in AC circuits? A) Capacitors increase the voltage in AC circuits. B) Capacitors only store energy in DC circuits. C) Capacitors store and release energy, influence phase relationships, and filter signals in AC circuits. D) Capacitors are used solely for power generation in AC circuits. Show Answer Correct Answer: C) Capacitors store and release energy, influence phase relationships, and filter signals in AC circuits. 29. Which of the following is an example of direct current? A) Current in a light bulb. B) Electricity from a power plant. C) Current in a battery-powered flashlight. D) Current in a home outlet. Show Answer Correct Answer: C) Current in a battery-powered flashlight. 30. Which of the following components of an AC circuit opposes the change in current by dropping a voltage? A) Power source. B) Capacitor. C) Resistor. D) Inductor. Show Answer Correct Answer: D) Inductor. 31. An instrument that displays AC waveforms graphically is a A) Ammeter. B) Wave meter. C) Oscilloscope. D) None of the above. Show Answer Correct Answer: C) Oscilloscope. 32. The phase difference between voltage and current in a purely resistive circuit A) -90. B) 90. C) O. D) 180. Show Answer Correct Answer: C) O. 33. In AC circuit, true power depends on: A) Current only. B) Voltage only. C) Power factor. D) Frequency only. Show Answer Correct Answer: C) Power factor. 34. What are the factors that can affect the power factor of an AC circuit? A) Reactive components, harmonic distortion, and load type. B) Wire color, circuit length, and insulation type. C) Phase angle, frequency, and power rating. D) Voltage, current, and resistance. Show Answer Correct Answer: A) Reactive components, harmonic distortion, and load type. 35. When the frequency of an AC circuit is doubled, then the capacitive reactance will be ..... A) Halved. B) Squared. C) Doubled. D) Tripled. Show Answer Correct Answer: A) Halved. 36. Sharpness of Resonance is measured by A) $\frac{\omega}{LC}$. B) $\frac{\omega R}{L}$. C) $\frac{2\omega}{\Lambda\omega}$. D) $\frac{\omega}{2\Lambda\omega}$. Show Answer Correct Answer: D) $\frac{\omega}{2\Lambda\omega}$. 37. The power factor is 1 for A) LR circuit. B) Inductive circuit. C) Capacitive circuit. D) LCR circuit in resonance. Show Answer Correct Answer: D) LCR circuit in resonance. 38. What is the formula for calculating the total impedance in a series RLC circuit? A) Z = R + j(XL-XC). B) Z = R + j(XC-XL). C) Z = R + XL + XC. D) Z = R + j(XL + XC). Show Answer Correct Answer: A) Z = R + j(XL-XC). 39. What is the cosine of the phase angle in an AC circuit known as? A) Resonance. B) Power Factor. C) Reactance. D) Phase Difference. Show Answer Correct Answer: B) Power Factor. 40. The region around a magnet where the magnetic forces act is the ..... A) Magnetic field. B) Electromagnetic pole. C) Magnetic domain. D) Magnetic pole. Show Answer Correct Answer: A) Magnetic field. 41. How does a capacitor react to AC? A) As the amplitude increases, the reactance decreases. B) As the amplitude increases, the reactance increases. C) As the frequency increases, the reactance increases. D) As the frequency increases, the reactance decreases. Show Answer Correct Answer: D) As the frequency increases, the reactance decreases. 42. A family wants to reduce the risk of AC hazards in their home. Which plan would be most effective? A) Ignore damaged wires. B) Regularly check and replace faulty cords, use circuit breakers, and keep water away from outlets. C) Use more extension cords. D) Place appliances near sinks. Show Answer Correct Answer: B) Regularly check and replace faulty cords, use circuit breakers, and keep water away from outlets. 43. What is the effect of increasing resistance on the current in an R.L series circuit? A) Increasing resistance has no effect on the current in an R.L series circuit. B) Increasing resistance decreases the current in an R.L series circuit. C) Increasing resistance causes the current to fluctuate in an R.L series circuit. D) Increasing resistance increases the current in an R.L series circuit. Show Answer Correct Answer: B) Increasing resistance decreases the current in an R.L series circuit. 44. State whether the following statements is TRUE or FALSE;The various possible frequencies of electromagnetic field waves form a spectrum. A) True. B) False. C) All the above. D) None of the above. Show Answer Correct Answer: A) True. 45. The product of the source voltage and the total current is ..... A) The power factor. B) True power. C) Reactive power. D) Apparent power. Show Answer Correct Answer: D) Apparent power. 46. The unit used for capacitive reactance and inductive reactance is A) Joule. B) Ampere. C) Ohm. D) Volt. Show Answer Correct Answer: C) Ohm. 47. State whether the following statement is TRUE or FALSE; Electromagnetic waves require a medium to propagate. A) TRUE. B) FALSE. C) All the above. D) None of the above. Show Answer Correct Answer: B) FALSE. 48. In an alternating current circuit consisting of elements in series, the current increases on increasing the frequency of supply. Which of the following elements are likely to constitute the circuit? A) Only resistor. B) Resistor and inductor. C) Resistor and capacitor. D) Only inductor. Show Answer Correct Answer: C) Resistor and capacitor. 49. What is the role of a fuse in an AC circuit? A) A fuse protects the circuit by breaking the connection when current exceeds a certain level. B) A fuse amplifies the current in the circuit. C) A fuse is used to convert AC to DC. D) A fuse has no effect on circuit safety. Show Answer Correct Answer: A) A fuse protects the circuit by breaking the connection when current exceeds a certain level. 50. An alternating current source of frequency 100 Hz is joined to a combination of a resistance, a capacitance and a coil in series. The potential difference across the coil, the resistance and the capacitor is 46, 8 and 40 volt respectively. The electromotive force of alternating current source in volt is ..... A) 76. B) 14. C) 10. D) 94. Show Answer Correct Answer: C) 10. 51. In a series RLC circuit, what occurs at resonance? A) Current is at its minimum. B) Power factor is zero. C) Voltage and current are in phase. D) Impedance is at its maximum. Show Answer Correct Answer: C) Voltage and current are in phase. 52. What is the primary difference between AC and DC? A) DC has a variable voltage. B) AC has a constant voltage. C) AC flows in one direction. D) DC flows in one direction. Show Answer Correct Answer: D) DC flows in one direction. 53. Hot wire ammeters can measure A) Only ac. B) Only dc. C) Both ac and dc. D) Neither ac nor dc. Show Answer Correct Answer: C) Both ac and dc. 54. In a circuit containing resistance only, the voltage and current are ..... with oneanother. A) Full rotation. B) Within range. C) In phase. D) Together. Show Answer Correct Answer: C) In phase. 55. Which quantity determines opposition offered by AC due to inductance? A) Resistance. B) Inductive reactance. C) Capacitance. D) Power factor. Show Answer Correct Answer: B) Inductive reactance. 56. Which household device converts AC to DC for its operation? A) Electric kettle. B) Laptop charger. C) Ceiling fan. D) Toaster. Show Answer Correct Answer: B) Laptop charger. 57. Describe the behavior of an inductor in an AC circuit. A) An inductor in an AC circuit causes the current to lead the voltage by 90 degrees. B) An inductor in an AC circuit causes the current to lag behind the voltage by 90 degrees and opposes changes in current. C) An inductor in an AC circuit has no effect on the phase relationship between current and voltage. D) An inductor in an AC circuit allows current to flow freely without any opposition. Show Answer Correct Answer: B) An inductor in an AC circuit causes the current to lag behind the voltage by 90 degrees and opposes changes in current. 58. Explain the phase difference between voltage and current in an inductive circuit. A) Voltage and current are in phase with each other. B) The current leads the voltage by 90 degrees. C) In an inductive circuit, the current lags the voltage by 90 degrees. D) The current lags the voltage by 180 degrees. Show Answer Correct Answer: C) In an inductive circuit, the current lags the voltage by 90 degrees. 59. Explain the concept of RMS voltage in an AC circuit. A) RMS voltage is the average of instantaneous voltages in an AC circuit. B) RMS voltage is the total voltage in a DC circuit. C) RMS voltage is the effective voltage in an AC circuit, calculated as the square root of the average of the squares of instantaneous voltages. D) RMS voltage is the peak voltage in an AC circuit. Show Answer Correct Answer: C) RMS voltage is the effective voltage in an AC circuit, calculated as the square root of the average of the squares of instantaneous voltages. 60. The current/voltage that changes direction with time are A) AC current. B) DC current. C) All the above. D) None of the above. Show Answer Correct Answer: A) AC 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 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 9 🏠 Back to Homepage 📘 Download PDF Books 📕 Premium PDF Books