MCQs On Alternating Current (A.C) for NEET pdf

Here we prepared a comprehensive Alternating Current MCQ for NEET Pdf form. These MCQ question on alternating current Class 12 chapter 7 for NEET are based on questions asked in different medical entrance exam like AIIMS, JIPMER, and NEET and other state level medical entrance exam. All Alternating Current (A.C) MCQs NEET Questions and Answers in the given below are prepared from previous year papers of all most all entrance exam. We have prepared Alternating Current (A.C) MCQs NEET previous year Questions separately. Take a Look Below

Important points to remember about Alternating current (A.C) 

• Voltage or current is said to be alternating if it changes continously in magnitude and perodically in direction.
• It can be represented by a sine curve or cosine curve.
• The maximum value of current in either direction is called peak value or the amplitude of current. It is represented by I0 Peak to peak value = 2I0
• The time taken by alternating current to complete one cycle of variation is called periodic time or time period of the current.
• The number of cycle completed by an alternating current in one second is called the frequency of the current. UNIT : (cycle/s) or (Hz).
• The mean value of A.C over any half cycle (either positive or negative) is that value of DC which would send same amount of charge through a circuit as is sent by the AC through same circuit in the same time.
• It is value of DC which would produce same heat in given resistance in given time as is done by the alternating current when passed through the same resistance for the same time.
• Alternating current and voltages are measured by a.c. ammeter and a.c. voltmeter respectively.
• Working of these instruments is based on heating effect of current, hence they are also called hot wire instruments.
• A.C. is cheaper than D.C
• It can be easily converted into D.C. (by rectifier)
• It can be controlled easily (choke coil)
• It can be transmitted over long distance at low power loss.
• It can be stepped up or stepped down with the help of transformer.
• The instrument based on heating effect of current are works on both A.C and D.C supply and also provides same heating for same value of A.C (rms) and D.C. that’s why a bulb bright equally in D.C. and A.C. of same value.
• If the frequency of AC is f then it becomes zero, 2f times in one second and the direction of current changes 2f times in one second. Also it become maximum 2f times in one second.
• Some Important wave forms and their RMS and Average Value

Multiple Choice Questions On Alternating Current (A.C) For NEET

1.If an A.C. main supply is given to be 220 V. What you would be the average e.m.f. during a positive half cycle__________

(a) 198 V

(b) 386 V

(c) 256 V

(d) None of these

Answer: C

2. The hot wire ammeter measures________

(a) D.C. current

(b) A.C. current

(c) None of above

(d) both (1) & (2)

Answer: D

3. Frequency of A.C. in India is__________

(a) 45 Hz

(b) 60 Hz

(c) 50 Hz

(d) None of the above

Answer: A

4. The resistance that must be connected in series with inductance of 0.2 H in order that the phase difference between current and e.m.f. may be 45°when the frequency is 50 Hz, is_________

(a) 6.28 ohm.

(b) 62.8 ohm.

(c) 628 ohm.

(d) 31.4 ohm.

Answer: B

5. An inductive circuit contains resistance of 10 ohms and an inductance of 20 H. If an A.C. voltage of 120 volt and frequency 60 Hz is applied to this circuit, the current would be nearly__________

(a) 0.016 amp.

(b) 0.16 amp.

(c) 0.48 amp.

(d) 0.80 amp.

Answer: A

6. A student connects a long air cored – coil of mangan in wire to a 100 V D.C. supply and records a current of 25 amp. When the same coil is connected across 100 V. 50 Hz a.c. the current reduces to 20 A , the reactance of the coil is____________

(a) 4 W

(b) 3 W

(c) 5 W

(d) None of the above

Answer: B

7. Alternating current is flowing in inductance L and resistance R. The frequency of source is ω/2p.Which of the following statement is correct_________

(a) For low frequency the limiting value of

impedance is L.

(b) For high frequency the limiting value of

impedance is ω/ L

(c) For high frequency the limiting value of

impedance is R.

(d) For low frequency the limiting value of

impedance is ωL

Answer: B

8. A circuit contains R, L and C connected in series with an A. C. source. The values of the reactances for inductor and capacitor are 200Ω and 600 Ω respectively and the impedance of the circuit is Z1 . What happens to the impedance of the same circuit if the values of the reactances are interchanged____________

(a) The impedance will remain unchanged

(b) The impedance will increase

(c) The impedance will decrease

(d) Information insufficient

Answer: A

9. When V = 100 sinwt is applied across a series (R-L-C) c100uit, At resonance the current in retance (R=100 Ω) is i = i0 sinωt, then power dissipation in circuit is________

(a) 50 W

(b) 100 W

(c) 25 W

(d) Can’t be calculated

Answer: A

10. At resosnance in a series LCR circuit, which of the following statements is true______

(a) Current in the circuit is maximum and phase difference between E and I is π/2

(b) Current in the circuit is maximum and phase difference between E and I is zero

(c) Voltage is maximum and phase difference between E and I is π/2

(d) Current is minimum and phase difference between E and I is zero

Answer: B

11. An alternating voltage is connected in series with a resistance r and an inductance L. If the potential drop across the resistance is 200 volt and across the inductance is 150 volt, the applied voltage___________

(a) 350 volt

(b) 250 volt

(c) 500 volt

(d) 300 volt

Answer: B

12. Phase of current in LCR circuit__________

(a) Is in the phase of potential

(b) Leading from the phase of potential

(c) Lagging from the phase of potential

(d) Before resonance frequency, leading from the phase of potential and after resonance

frequency, lagging from the phase of potential

Answer: D

13. In LCR circuit, the voltage across the terminals of a resistance, inductance &capacitance are 40V, 30V & 60V, then the voltage across the main source will be –

(a) 130 volt

(b) 100 volt

(c) 70 volt

(d) 50 volt

Answer: D

14. A bulb and a capacitor are connected in series to a source of alternating current. If its frequency is increased, while keeping the voltage of the source constant, then_______

(a) Bulb will give more intense light.

(b) Bulb will give less intense light.

(c) Bulb will give light of same intensity as before

(d) Bulb will stop radiating light.

Answer: A

15. Which of the following device in alternating circuit provides maximum power?

(a) Only capacitor

(b) Capacitor and resistor

(c) Only inductor

(s) Only resistor

Answer: D

16. A LC circuit is in the state of resonance. if C = 0.1 mF and L = 0.25 henry. Neglecting ohmic resistance of circuit what is the frequency of

oscillations_______

(a) 1007 Hz

(b) 100 Hz

(c) 109 Hz

(d) 500 Hz

Answer: A

17. A 60 µF capacitor is charged to 100 volts. This charged capacitor is connected across a 1.5 mH coil, so that LC oscillations occur. The maximum current in the coil is _________

(a) 1.5 A

(b) 2 A

(c) 15 A

(d) 20 A

Answer: D

18. A coil of self-inductance L is connected in series with a bulb B and an AC source. Brightness of the bulb decreases when__________

(a) an iron rod is inserted in the coil.

(b) frequency of the AC source is decreased.

(c) number of turns in the coil is reduced.

(d) A capacitance of reactance XC = XL

is included

in the same circuit.

Answer: A

19. If mechanical system is equivalent to electrical system then ‘x’ is analogous to________

(a) Charge

(b) Current

(c) Electic field

(d) Voltage

Answer: A

20. In series RLC a.c. circuit, L = 1 H, C = 1 µF and R = 20W is connected across a supply voltage of 10 volt. At resonance, voltage across L is ______

(a) 500 V

(b) 200 V

(c) 300 V

(d) 100 V

Answer: A

21. When 100 volts d.c. is applied across a solenoid a current of 1.0 amp. flows in it. When 100 volt a.c. is applied across the same coil, the current drops to 0.5 amp. If the frequency of the a.c. source is 50 Hz the impedance and inductance of the sole-noid are ____________

(a) 200 ohm and 0.55 H

(b) 100 ohm and 0.86 H

(c) 200 ohm and 1.0 H

(d) 100 ohm and 0.93 H

Answer: A

22. A 1.5 µF capacitor is charged of 60 V. The charging battery is then disconnected and a 15 mH coil is connected in series with the capacitor so that LC oscillations occurs. Assuming that the circuit contains no resistance. The maximum current in this coil shall be close to________________

(a) 1.4 A

(b) 1.2 A

(c) 0.8 A

(d) 0.6 A

Answer: D

23. A capacitor of capacitance 2 mF is connected in the tank circuit of an oscillator oscillating with a frequency of 1 kHz. If the current flowing in the circuit is 2 mA,the voltage across the capacitor will be________

(a) 0.16 V

(b) 0.32 V

(c) 79.5 V

(d) 159 V

Answer: A

24. If frequency of alternating source is made zero then which of the following statement is true _______

(a) Current through capacitor will be zero

(b) Current through resistance will be zero

(c) Current through inductance will be zero

(d) All

Answer: A

25. The self inductance of a choke coil is 10 mH. when it is connected with a 10 V D.C. source, then the loss of power is 20 watt. When it is connected with 10 volt A.C. source loss of power is 10 watt. Thef frequency of A.C. source will be_________

(a) 50 Hz

(b) 60 Hz

(c) 80 Hz

(d)100 Hz

Answer: C

26 If a step up transformer have turn ratio 5, frequency 50 Hz root mean square value of potential difference on primary 100 volts and the resistance of the secondary winding is 500 W then the peak value of voltage in secondary winding will be (the efficiency of the transformer is hundred percent)

(a) 500 √2

(b) 10 √2

(c) 50 √2

(d) 20 √2

Answer: A