This quiz works best with JavaScript enabled. Home > Class 12 > Class 12 Physics (Part I) Chapter 7 Alternating Current – Quiz 26 🏠 Homepage 📘 Download PDF Books 📕 Premium PDF Books Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 26 (25 MCQs) Quiz Instructions Select an option to see the correct answer instantly. 1. What is a current that fluctuates back and forth within a circuit called? A) Direct Current. B) Alternating Current. C) Oscillating Current. D) Static Current. Show Answer Correct Answer: C) Oscillating Current. 2. The resistance of a coil for d.c. is in ohms .In a.c., the resistance A) Will remain same. B) Will increase. C) Will decrease. D) Will be zero. Show Answer Correct Answer: B) Will increase. 3. How many alternations are completed when the conductor passes one pair of magnetic poles? A) One alternation. B) Two alternations. C) Three alternations. D) Four alternations. Show Answer Correct Answer: B) Two alternations. 4. The primary of a 3:1 step-up transformer is connected to a source and the secondary is connected to a resistor R. The power dissipated by R in this situation is P. If R is connected directly to the source it will dissipate a power of: A) P/9. B) P/3. C) 3P. D) 9P. Show Answer Correct Answer: A) P/9. 5. The alternating current is the flow of electric current whose A) Always change its magnitude. B) Have random change of magnitude and direction. C) Periodically change its magnitude and direction. D) Always change its direction. Show Answer Correct Answer: C) Periodically change its magnitude and direction. 6. Fill in the blank:Hair growth will be softer to the ..... A) Touch. B) Eye. C) Smell. D) Taste. Show Answer Correct Answer: A) Touch. 7. What is the significance of the phasor representation in AC analysis? A) It complicates the calculations of AC circuits. B) Phasor representation is only useful for DC analysis. C) Phasor representation simplifies AC analysis by converting sinusoidal signals into complex numbers, facilitating easier calculations and visualization of phase relationships. D) Phasors are used to represent non-sinusoidal signals. Show Answer Correct Answer: C) Phasor representation simplifies AC analysis by converting sinusoidal signals into complex numbers, facilitating easier calculations and visualization of phase relationships. 8. In a R, L, C circuit, three elements are connected in series by a.c. source. If frequency is less than resonating frequency, then net impedance of the circuit will be A) Capacitive. B) Inductive. C) Pure resistive. D) None of these. Show Answer Correct Answer: A) Capacitive. 9. What is the waveform called that results from the graphing of values produced by the motion of the conductor? A) Pulse wave. B) Sine wave. C) Triangle wave. D) Square wave. Show Answer Correct Answer: B) Sine wave. 10. ..... is the rate at which current changes direction per second A) Frequency. B) Cycle. C) All the above. D) None of the above. Show Answer Correct Answer: A) Frequency. 11. What is another name for alternating current? A) Radio frequency RF. B) Direct current DC. C) Static electricity. D) Electromagnetic induction. Show Answer Correct Answer: A) Radio frequency RF. 12. Consider the following statements and then select the true/false statements.1. Most of the electrical device we require ac voltage2. Most of the electrical energy sold by power companies is transmitted and distributed as alternating current3. AC voltage can be easily and efficiently converted from one to the other by means of transformers. A) T, F, F. B) T, F, T. C) T, T, F. D) T, T, T. Show Answer Correct Answer: D) T, T, T. 13. When a.c. is applied to a purely capacitive circuit, what is the phase relation between current and emf? A) Current leads emf by $\pi/2$. B) Current lags emf by $\pi/2$. C) Current and emf are in phase. D) Current leads emf by $\pi/4$. Show Answer Correct Answer: A) Current leads emf by $\pi/2$. 14. An alternating voltage has the equation v = 141.4 sin 377t . Determine the frequency. A) 40 Hz. B) 50 Hz. C) 60 Hz. D) 70 Hz. Show Answer Correct Answer: C) 60 Hz. 15. What is the effect of frequency on the reactance of an inductor? A) The reactance of an inductor is independent of the circuit configuration. B) The reactance of an inductor increases with frequency. C) The reactance of an inductor remains constant regardless of frequency. D) The reactance of an inductor decreases with frequency. Show Answer Correct Answer: B) The reactance of an inductor increases with frequency. 16. The unit of frequency is A) Cycle. B) Cycle-second. C) Hertz/second. D) Hertz. Show Answer Correct Answer: D) Hertz. 17. The electric current in a circuit is given by $i=i_o\left(\frac{t}{\tau}\right)$ $t=0$ $t=\tau$ A) $\frac{i_o}{\sqrt{3}}$. B) $\frac{i_o}{\sqrt{2}}$. C) $\frac{2i_o}{\sqrt{3}}$. D) $\frac{\sqrt{2}i_o}{3}$. Show Answer Correct Answer: A) $\frac{i_o}{\sqrt{3}}$. 18. One complete wave form including positive half cycle and negative half cycle is called A) Cycle. B) Frequency. C) All the above. D) None of the above. Show Answer Correct Answer: A) Cycle. 19. How is the power in a three-phase system calculated? A) $P = VI$. B) $P = \sqrt{3} \times VI \times\cos(\phi)$. C) $P = V^2/R$. D) $P = I^2R$. Show Answer Correct Answer: B) $P = \sqrt{3} \times VI \times\cos(\phi)$. 20. When frequency decreases, capacitive reactance ..... A) Increases. B) Decreases. C) Remains the same. D) May increase or decrease. Show Answer Correct Answer: A) Increases. 21. What in causes a lightbulb to flicker? A) Alternating Currents. B) Direct Currents. C) All the above. D) None of the above. Show Answer Correct Answer: A) Alternating Currents. 22. A capacitor of 50 pF is connected to an a.c source of frequency 1kHz. Calculate its reactance A) 3.1x10$^{6}$ Hz. B) 2.1x10$^{6}$ Hz. C) 1.1x10$^{6}$ Hz. D) 0.1x10$^{6}$ Hz. Show Answer Correct Answer: A) 3.1x10$^{6}$ Hz. 23. The total voltage transmitted from the plant is A) 7 kV. B) 3 kV. C) 4 kV. D) 0.5 kV. Show Answer Correct Answer: A) 7 kV. 24. What does the root mean square (r.m.s.) voltage represent? A) The voltage at the midpoint of the cycle. B) The average of all instantaneous voltages. C) The effective value of the alternating voltage. D) The peak voltage divided by two. Show Answer Correct Answer: C) The effective value of the alternating voltage. 25. The total opposition to current flow in an AC circuit is known as ..... A) Resistance. B) Impedance. C) Capacitive reactance. D) Inductive reactance. Show Answer Correct Answer: B) Impedance. ← PreviousNext →Related 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 8Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 9Class 12 Physics (Part I) Chapter 7 Alternating Current Quiz 10 🏠 Back to Homepage 📘 Download PDF Books 📕 Premium PDF Books