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 6 🏠 Homepage 📘 Download PDF Books 📕 Premium PDF Books Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 6 (60 MCQs) Quiz Instructions Select an option to see the correct answer instantly. 1. One type of nonsinusoidal waveform is the ..... A) Square wave. B) Sine wave. C) Peak wave. D) Phase angle wave. Show Answer Correct Answer: A) Square wave. 2. What is the key feature of alternating current? A) The current is measured in Hertz. B) The current only moves in one direction. C) The current constantly changes direction. D) The current is shown on an oscilloscope. Show Answer Correct Answer: C) The current constantly changes direction. 3. In a series RLC circuit, derive the expression for the total voltage across the circuit components $V_{total}$ A) $V_{total} = \dfrac{P}{I}$. B) $V_{total} = V_{R} + V_{L} + V_{C}$. C) $V_{total} = I\cdot Z$. D) $V_{total} = \sqrt{V_{R}^{2} + (V_{L}-V_{C})^{2}}$. Show Answer Correct Answer: D) $V_{total} = \sqrt{V_{R}^{2} + (V_{L}-V_{C})^{2}}$. 4. Electrical energy is transferred through ..... in a transformer. A) Rotor. B) Electromagnetic field. C) Electric field. D) Air space. Show Answer Correct Answer: B) Electromagnetic field. 5. Which does not allow DC to pass through? A) DIODE. B) CAPACITOR. C) RESISTOR. D) INDUCTOR. Show Answer Correct Answer: B) CAPACITOR. 6. In frequency modulation, the amplitude of carrier waves is: A) Increases. B) Remains constant. C) Decreases. D) None of these. Show Answer Correct Answer: B) Remains constant. 7. If the time for one cycle is 0.1 second, the frequency is ..... A) 0.5Hz. B) 10Hz. C) 0.1Hz. D) 1Hz. Show Answer Correct Answer: B) 10Hz. 8. What happens to the induced current when there is relative motion between a conductor and magnetic field lines? A) It is produced. B) It decreases. C) It becomes constant. D) It stops. Show Answer Correct Answer: A) It is produced. 9. Those statement describe period except A) Unit = second. B) Time required for a sine wave to complete one full cycle. C) It is equal to frequency. D) T = 1/f. Show Answer Correct Answer: C) It is equal to frequency. 10. What is the effect of inductance on AC current? A) Inductance causes the AC current to lead the voltage. B) Inductance increases the effective current without changing impedance. C) Inductance has no effect on AC current. D) Inductance causes the AC current to lag behind the voltage, increasing impedance and reducing effective current. Show Answer Correct Answer: D) Inductance causes the AC current to lag behind the voltage, increasing impedance and reducing effective current. 11. High potential voltage produced by three-phase generators commonly used in A) Anode. B) Filament. C) X-ray tube. D) Transformer. Show Answer Correct Answer: C) X-ray tube. 12. What is the typical frequency of AC used in Great Britain? A) 60 Hz. B) 120 Hz. C) 100 Hz. D) 50 Hz. Show Answer Correct Answer: D) 50 Hz. 13. An ac voltage $\varepsilon = \varepsilon_{0} \sin \omega t$ $C$ $i$ A) $i = i_{m}\cos \omega t$. B) $i = i_{m} \sin (\omega t-\pi/2)$. C) $i = i_{m} \sin (\omega t + \pi/2)$. D) $i = i_{m} \sin \omega t$. Show Answer Correct Answer: C) $i = i_{m} \sin (\omega t + \pi/2)$. 14. Describe the function of a transformer in electrical circuits. A) A transformer converts AC to DC power. B) A transformer changes voltage levels in electrical circuits. C) A transformer increases current levels in electrical circuits. D) A transformer stores electrical energy for later use. Show Answer Correct Answer: B) A transformer changes voltage levels in electrical circuits. 15. At resonance frequency ..... A) Impedene is zero, rms current flow is maximum. B) Impedence is minimum, rms current flow is maximum. C) Impedence is maximum, rms current flow is minimum. D) Impedence is increasing, rms current flow is decreasing. Show Answer Correct Answer: B) Impedence is minimum, rms current flow is maximum. 16. Fill in the blank:Hair growth will be finer in ..... A) Color. B) Volume. C) Length. D) Texture. Show Answer Correct Answer: D) Texture. 17. What is a sine wave and how is it related to AC? A) A sine wave is a random fluctuation in voltage. B) A sine wave is a square wave used in digital circuits. C) A sine wave is a smooth periodic oscillation that represents the voltage and current in alternating current (AC) systems. D) A sine wave is a type of direct current (DC) signal. Show Answer Correct Answer: C) A sine wave is a smooth periodic oscillation that represents the voltage and current in alternating current (AC) systems. 18. Define reactance in the context of AC circuits. A) Reactance is the power factor of an AC circuit. B) Reactance is the measure of voltage in a circuit. C) Reactance is the opposition to AC current caused by inductance and capacitance. D) Reactance is the total resistance in a DC circuit. Show Answer Correct Answer: C) Reactance is the opposition to AC current caused by inductance and capacitance. 19. (c) How long does one cycle of this ac supply last? A) 0.2 s. B) 2 s. C) 0.02 s. D) 5 s. Show Answer Correct Answer: C) 0.02 s. 20. What happens if the live wire touches the metal case of an appliance? A) The appliance will work normally. B) The appliance will become live and dangerous. C) The appliance will stop working. D) The appliance will become insulated. Show Answer Correct Answer: B) The appliance will become live and dangerous. 21. An alternating voltage is described by $V=240\sin400t$ $V$ A) 250 V. B) 340 V. C) 170 V. D) 240 V. Show Answer Correct Answer: C) 170 V. 22. What is the formula to calculate the RMS voltage from the peak voltage? A) Vrms = Vmax x 1.414. B) Vrms = Vmax x 2. C) Vrms = Vmax x 0.5. D) Vrms = Vmax x 0.707. Show Answer Correct Answer: D) Vrms = Vmax x 0.707. 23. Based on the phasor diagram of RL circuit. The rms supply voltage V (or total voltage) of the circuit is given by A) The sum of all voltage in the circuit. B) The sum of the squares of voltage across R and L. C) The square root of the sum of the squares of the voltage across R and L,. D) The square root of the sum of all voltage in the circuit. Show Answer Correct Answer: C) The square root of the sum of the squares of the voltage across R and L,. 24. Opening the secondary circuit of a current transformer under load will cause a dangerous level of ..... A) Low impedance. B) High impedance. C) Induced high voltage. D) Induced high current. Show Answer Correct Answer: C) Induced high voltage. 25. What is the voltage level for heavy industry supply in the UK? A) 50kV or 25kV. B) 100kV or 50kV. C) 66kV or 33kV. D) 33kV or 11kV. Show Answer Correct Answer: D) 33kV or 11kV. 26. The frequency of an alternating current is A) The number of electrons passing through a point in one second. B) The number of waves passing through a point in one second. C) The number of cycles generated in one minute. D) The speed with which the alternator runs. Show Answer Correct Answer: B) The number of waves passing through a point in one second. 27. When an AC voltage of 220 V is applied to the capacitor C A) The maximum voltage between plates is 220 V. B) The charge on the plates is in phase with the applied voltage. C) The current is in phase with the applied voltage. D) Power delivered to the capacitor is zero. Show Answer Correct Answer: D) Power delivered to the capacitor is zero. 28. Why use AC for electricity supply? A) All of the above. B) It can be transformed to high voltages. C) It has lower power losses in transmission lines. D) It can work equally well with DC. Show Answer Correct Answer: A) All of the above. 29. As the number of turns in the coil increases, what happens to the inductance of the coil? A) Increases. B) Remains the same. C) Becomes zero. D) Decreases. Show Answer Correct Answer: A) Increases. 30. A bulb is connected first with dc and then ac of same voltage then it will shine brightly with A) A.c. B) D.c. C) Brightness will be in ratio 1/(1.4). D) Equally with both. Show Answer Correct Answer: D) Equally with both. 31. In an RC, RL or RCL circuit, the total opposition to alternating current is called as A) Resistance. B) Reactant. C) Phase angle. D) Impedence. Show Answer Correct Answer: D) Impedence. 32. Complete the sentence:The ..... wire is connected to the longest pin in a plug. A) Live. B) Neutral. C) Earth. D) None. Show Answer Correct Answer: C) Earth. 33. When an alternating current passes through a conductor then the direction of A) Current remains constant. B) Voltage remains constant. C) Both the current and voltage changes. D) Current remains constant but direction of voltage changes. Show Answer Correct Answer: C) Both the current and voltage changes. 34. Which of the following is a commonly used term related to alternating current? A) Static electricity. B) Direct voltage. C) Resistance. D) Frequency. Show Answer Correct Answer: D) Frequency. 35. The instantaneous current in an ac circuit is I = 2.0 sin 314 twhat is rms value of the current? A) 2 A. B) 1 / 1.414 A. C) 1 A. D) 1.414 A. Show Answer Correct Answer: D) 1.414 A. 36. What is the primary function of a diode bridge in an AC circuit? A) To store energy. B) To allow current to flow in one direction. C) To increase the voltage. D) To convert AC to DC. Show Answer Correct Answer: D) To convert AC to DC. 37. The opposition to AC current flow presented by capacitors and inductors taken together is called: A) Resistance. B) Impedance. C) Reluctance. D) Reactance. Show Answer Correct Answer: D) Reactance. 38. The value of output voltage in the secondary coil is A) 12 V. B) 1.2 V. C) 6 V. D) 3 V. Show Answer Correct Answer: B) 1.2 V. 39. The type of current where charges shake back and forth in a circuit A) Alternating Current. B) Voltage. C) Direct Current. D) Switchback Current. Show Answer Correct Answer: A) Alternating Current. 40. Most office and domestic equipment such as TVs, audio systems, amplifiers, flash lights, computers, tablets and smartphones use A) AC power. B) DC power. C) All the above. D) None of the above. Show Answer Correct Answer: A) AC power. 41. What does RC stand for? A) Radio Control. B) Rotary Club. C) Resistor Capacitor. D) Remote Control. Show Answer Correct Answer: C) Resistor Capacitor. 42. How is phase difference measured? A) Phase difference is measured in volts. B) Phase difference is measured in hertz. C) Phase difference is measured in degrees or radians. D) Phase difference is measured in meters. Show Answer Correct Answer: C) Phase difference is measured in degrees or radians. 43. What is the frequency of alternating current in the UK? A) 50 Hertz. B) Cannot be determined. C) 230 volts. D) Not mentioned. Show Answer Correct Answer: A) 50 Hertz. 44. The opposing force that an inductor presents to the flow of alternating current is called ..... A) Anti-current. B) Resistance. C) Inductive reactance. D) Inductive resistance. Show Answer Correct Answer: C) Inductive reactance. 45. A step-up transformer connected to a 220 V ac line is to supply 22 kV for a neon sign in secondary circuit. In primary circuit, a fuse wire is connected which is to blow when the current in the secondary circuit exceeds 10 mA. The turn ratio of the transformer is A) 150. B) 50. C) 200. D) 100. Show Answer Correct Answer: D) 100. 46. If the current changes from 20A to 10A in 5 seconds and the value of inductance is 1H, calculate the emf induced. A) 6V. B) 2V. C) 4V. D) 8V. Show Answer Correct Answer: B) 2V. 47. What is the maximum phase difference possible in an AC circuit? A) 180 degrees. B) 270 degrees. C) 90 degrees. D) 360 degrees. Show Answer Correct Answer: A) 180 degrees. 48. The formula for calculating the RMS value of a waveform is A) Vrms=.707*Vpeak. B) Vrms=1.414*Vpeak. C) All the above. D) None of the above. Show Answer Correct Answer: A) Vrms=.707*Vpeak. 49. A transformer with 10 turns in the primary and two turns in the secondary has a turns ratio of ..... A) 8:1. B) 20:1. C) 10:1. D) 5:1. Show Answer Correct Answer: D) 5:1. 50. How does a transformer work in an AC circuit? A) A transformer converts DC to AC voltage directly. B) A transformer generates electricity using solar power. C) A transformer stores electrical energy in batteries. D) A transformer transfers electrical energy between two or more circuits through electromagnetic induction in an AC circuit. Show Answer Correct Answer: D) A transformer transfers electrical energy between two or more circuits through electromagnetic induction in an AC circuit. 51. What is the best method of treating the lower hair follicle to render the follicle inactive or weaken its ability to reproduce new hair growth? A) Exposing the follicle to ultraviolet light therapy. B) Applying topical creams to the surface of the skin. C) Massaging the area with essential oils. D) Using thermal heat or damage to the germinative tissue through short wave diathermy (electro-coagulation). Show Answer Correct Answer: D) Using thermal heat or damage to the germinative tissue through short wave diathermy (electro-coagulation). 52. The value of current in the circuit is A) 14 A. B) 6.28 A. C) 5 A. D) 9.46 A. Show Answer Correct Answer: D) 9.46 A. 53. AC generator is used to A) Convert low voltage into high voltage. B) High voltage into low voltage. C) Mechanical energy into electrical energy. D) All of the above. Show Answer Correct Answer: C) Mechanical energy into electrical energy. 54. Disadvantages of DC are A) High cost when dealing with high current systems; i.e. larger cables, fuses, switches and other components required for high current, low voltage applications. B) Difficult to obtain DC appliances and equipment. C) Higher chances of fire hazards when maximum circuit ratings and wire sizes are not strictly adhered to. D) All the above. Show Answer Correct Answer: D) All the above. 55. At what voltage is electricity typically supplied to domestic users in the UK? A) 110V. B) 230V. C) 500V. D) 400V. Show Answer Correct Answer: B) 230V. 56. The power factor of a good choke coil is ..... A) Nearly zero. B) Exactly zero. C) Nearly one. D) Exactly one. Show Answer Correct Answer: A) Nearly zero. 57. What happens to the temperature rise in a resistor when 1 amp of AC current passes through it compared to 1 amp of DC current? A) The temperature rise is higher with AC current. B) The temperature rise is lower with AC current. C) The temperature rise is the same for both AC and DC current. D) The temperature rise is zero with AC current. Show Answer Correct Answer: B) The temperature rise is lower with AC current. 58. Power factor of a purely inductive circuit is: A) 0.5. B) -1. C) 0. D) 1. Show Answer Correct Answer: C) 0. 59. A 15 $\mu$F capacitor is connected to a 220 V, 50 Hz source . Determine the capacitive reactance. A) 440 $\Omega$. B) 50 $\Omega$. C) 15 $\Omega$. D) 212 $\Omega$. Show Answer Correct Answer: D) 212 $\Omega$. 60. What is a type of electric current that reverses direction periodically over time? A) Direct currents. B) Alternating currents. C) All the above. D) None of the above. Show Answer Correct Answer: B) Alternating currents. ← 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 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