This quiz works best with JavaScript enabled. Home > Class 12 > Class 12 Physics (Part I) Chapter 7 Alternating Current – Quiz 1 🏠 Homepage 📘 Download PDF Books 📕 Premium PDF Books Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 1 (25 MCQs) Quiz Instructions Select an option to see the correct answer instantly. 1. A measurement taken from zero to the highest value obtained in either the positive or negative half of a sine wave would determine? . A) The effective voltage. B) The peak voltage. C) The peak to peak voltage. D) The average voltage. Show Answer Correct Answer: B) The peak voltage. 2. Transfer of electrical energy from one circuit to another without the aid of electrical connections A) Is called induction. B) Is called capacitance. C) Can cause excessive arcing and heat, and as a result is practical for use only with low voltages/amperages. D) None of the above. Show Answer Correct Answer: A) Is called induction. 3. Alternating current can not be measured by dc ammeter because A) Ac cannot pass through dc ammeter. B) Average value of complete cycle is zero. C) Ac is virtual. D) Ac changes its direction. Show Answer Correct Answer: B) Average value of complete cycle is zero. 4. A pure inductor of inductance 15 H is connected to an a.c.s source of frequency 100 Hz. If the r.m.s. value of the voltage is 12 V, what is the maximum instantaneous output power? A) 1.3 $\times10^{-3}W$. B) 1.5 $\times10^{-2}W$. C) 0 W. D) 1.5 W. Show Answer Correct Answer: B) 1.5 $\times10^{-2}W$. 5. In the transformer described (primary:2200 V, 5 A, 4000 turns; secondary:220 V output), what is the secondary current (ideal transformer)? A) 5 A. B) 10 A. C) 25 A. D) 50 A. Show Answer Correct Answer: D) 50 A. 6. What device is used to transform voltages in an a.c. system? A) Transformer. B) Rectifier. C) Inverter. D) Converter. Show Answer Correct Answer: A) Transformer. 7. In an LCR circuit if impedance is $\sqrt{2}$ A) Zero. B) $30^0$. C) $60^0$. D) $45^0$. Show Answer Correct Answer: D) $45^0$. 8. Complete the sentence:A cable is made up of two or three ..... covered by an outer layer of rubber or flexible plastic. A) Insulators. B) Conductors. C) Resistors. D) Capacitors. Show Answer Correct Answer: B) Conductors. 9. An inductor having negligible resistance and 50 mH self inductance and 500 pF capacitance are connected in AC circuit. The resonance frequency will be ..... A) 31.8 Hz. B) 31.8 kHz. C) 31.8 MHz. D) 31.8 GHz. Show Answer Correct Answer: B) 31.8 kHz. 10. Alternating current is transmitted to distant places A) At high voltage and Low current. B) At high voltage and high current. C) At low voltage and low current. D) At low voltage and high current. Show Answer Correct Answer: A) At high voltage and Low current. 11. For $f>fr$ A) Current and voltage are in same phase. B) Current is leading the voltage by $\frac{\pi}{2}$. C) Current is lagging by $\frac{\pi}{2}$. D) None of the above. Show Answer Correct Answer: C) Current is lagging by $\frac{\pi}{2}$. 12. In an AC circuit containing only a capacitor, current: A) Lags voltage by 90$^\circ$. B) Leads voltage by 90$^\circ$. C) Is in phase with voltage. D) Has zero phase difference at resonance. Show Answer Correct Answer: B) Leads voltage by 90$^\circ$. 13. What device generates alternating current by rotating a magnetic field? A) Transformer. B) Alternator. C) Rectifier. D) Battery. Show Answer Correct Answer: B) Alternator. 14. The time taken for one cycle of an alternating current is called the ..... A) Frequency. B) Period. C) Amplitude. D) Wavelength. Show Answer Correct Answer: B) Period. 15. Explain the concept of inductive reactance. A) Inductive reactance decreases with increasing frequency in a resistor. B) Inductive reactance is the resistance to DC current in a capacitor. C) Inductive reactance is the same as capacitive reactance in an inductor. D) Inductive reactance is the opposition to AC current in an inductor, increasing with frequency. Show Answer Correct Answer: D) Inductive reactance is the opposition to AC current in an inductor, increasing with frequency. 16. What role does inductive reactance play in AC circuits? A) Inductive reactance in AC circuits decreases with frequency. B) Inductive reactance in AC circuits opposes the change in current flow due to inductors and increases with frequency. C) Inductive reactance in AC circuits supports the change in current flow due to inductors. D) Inductive reactance in AC circuits has no effect on current flow. Show Answer Correct Answer: B) Inductive reactance in AC circuits opposes the change in current flow due to inductors and increases with frequency. 17. A homeowner wants to install a new AC-powered air conditioner. What should they consider to ensure safe installation? A) Use any available outlet regardless of its rating. B) Check the outlet voltage and current rating, use a dedicated circuit, and follow manufacturer instructions. C) Ignore the manufacturer's instructions. D) Use extension cords for permanent installation. Show Answer Correct Answer: B) Check the outlet voltage and current rating, use a dedicated circuit, and follow manufacturer instructions. 18. What is the total opposition of current flow in AC circuit? A) Capacitance reactance. B) Resistance. C) Inductive reactance. D) Impedance. Show Answer Correct Answer: D) Impedance. 19. The ac adapter for a laptop computer contains a transformer. The input of the adapter is the 120 volts from the ac wall outlet. The output from the transformer is 20 volts. What is the turns ratio of the transformer? A) 0.17. B) 6. C) 100. D) This cannot be determined without knowing how many turns one of the coils in the transformer has. Show Answer Correct Answer: B) 6. 20. Why should water be kept away from AC electrical outlets? A) Water increases resistance. B) Water can cause short circuits and electric shocks. C) Water makes appliances work faster. D) Water reduces voltage. Show Answer Correct Answer: B) Water can cause short circuits and electric shocks. 21. A transformer is used to light a 140 watt, 24 volt lamp from 240V ac mains. The current in the main cable is 0.44A. The efficiency of the transformer is A) 48%. B) 63.8%. C) 83.3%. D) 90%. Show Answer Correct Answer: C) 83.3%. 22. What is the value of the greatest induced EMF in either direction called? A) Instantaneous value. B) Average value. C) Peak value. D) Peak-to-peak value. Show Answer Correct Answer: C) Peak value. 23. The combination of resistance, capacitance and induntance is referred to A) Impedance. B) Reactance. C) Angular frequency. D) Amplitude. Show Answer Correct Answer: A) Impedance. 24. What is the unit of frequency for alternating current? A) Volts. B) Amperes. C) Hertz. D) Ohms. Show Answer Correct Answer: C) Hertz. 25. Which of the following is true about energy losses in AC transmission? A) Energy losses are higher in AC than in DC. B) Energy losses are lower in AC due to the ability to use high voltages. C) Energy losses are the same for both AC and DC. D) Energy losses are negligible in both AC and DC. Show Answer Correct Answer: B) Energy losses are lower in AC due to the ability to use high voltages. 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