JEE Physics Alternating Current MCQs Set A

Question: Hot wire ammeters are used for measuring

• a) Both AC and DC
• b) Only AC
• c) Only DC
• d) Neither AC nor DC

Answer: Both AC and DC

Question: In alternating current circuits, the a.c. meters measure

• a) r.m.s. value
• b) Peak value
• c) Mean value
• d) Mean square value

Answer: r.m.s. value

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: A 110 V d.c. heater is used on an a.c. source, such that the heat produced is same as it produces when connected to 110 V dc in same time-intervals. What would be the r.m.s. value of the alternating voltage?

• a) 110 V
• b) 220 V
• c) 330 V
• d) 440 V

Answer: 110 V

Question:

• a) 5 volt
• b) 10 volt
• c)

  

• d) 1 volt

Answer: 5 volt

Question: The time required for a 50 Hz sinusoidal alternating current to change its value from zero to the r.m.s. value

• a) 2.5 × 10^–3 s
• b) 10^–1 s
• c) 10^–6 s
• d) 1.5 × 10^–2 s

Answer:  2.5 × 10^–3 s

Question:

• a)

  

• b)

  

• c)

  

• d) None of these

Answer:

Question:

• a) 1.6 mA
• b) 26 mA
• c) 20 mA
• d) 5.5 mA

Answer: 1.6 mA

Question: An inductive circuit contains a resistance of 10 ohms and an inductance of 2 henry. If an alternating voltage of 120 V and frequency 60 Hz is applied to this circuit, the current in the circuit would be nearly

• a) 0.16 A
• b) 0.48 A
• c) 0.80 A
• d) 0.32 A

Answer: 0.16 A

More Questions..........................

Question: A coil and a bulb are connected in series with a 12 volt direct current source. A soft iron core is now inserted in the coil. Then

• a) The intensity of the bulb remains the same
• b) The intensity of the bulb increases
• c) The intensity of the bulb decreases
• d) Nothing can be said

Answer: The intensity of the bulb remains the same

Question: When 100 volt d.c. is applied across a solenoid, a current of 1.0 A flows in it. When 100 volt a.c. is applied across the same coil, the current drops to 0.5 A. If the frequency of a.c. source is 50 Hz the impedance and inductance of the solenoid is

• a) 200 ohm and 0.55 henry
• b) 100 ohm and 0.86 henry
• c) 200 ohm and 1.0 henry
• d) 100 ohm and 0.93 henry

Answer: 200 ohm and 0.55 henry

Question:

• a)

  

• b)

  

• c)

  

• d) None of these

Answer:

Question:

• a) 50
• b) 40
• c) 70
• d) 190

Answer: 50

Question:

• a)

  

• b)

  

• c) 400 V
• d) 1200 V

Answer:

Question:

• a) Zero, zero
• b) 10 A, 10 A
• c) 10 A, zero
• d) Zero, 10 A

Answer: Zero, zero

Question: In series LCR circuit, the phase difference between voltage across L and voltage across C is

• a)

  

• b)

  

• c)

  

• d) Zero

Answer:

Question: With increase in frequency of an a.c. supply, the impedance of an LCR series circuit

• a) Decreases at first, becomes minimum and then increases
• b) Increases
• c) Decreases
• d) Remains constant

Answer: Decreases at first, becomes minimum and then increases

Question: Mark the incorrect statemen

• a) The use of a capacitor is avoided in the circuit of an induction coil
• b) Power factor can often be improved by the use of a capacitor of appropriate capacitance in the circuit
• c) For circuits used for transporting electric power, a low power factor implies large power loss in transmission
• d) In any AC circuit, the applied instantaneous voltage equals to the algebraic sum of the instantaneous voltages across the series elements of the circuit.

Answer: The use of a capacitor is avoided in the circuit of an induction coil

Question:

• a) 2 A
• b) 3 A
• c) Zero
• d) 1 A

Answer: 2 A

Question:

• a) 1000
• b) 2000
• c) 500
• d) 250

Answer: 1000

Question:

• a) 500 rad/s
• b) 600 rad/s
• c) 800 rad/s
• d) 1000 rad/s

Answer: 500 rad/s

Question:

• a)

  

• b)

  

• c)

  

• d) None of these

Answer:

Question: Power factor of an ideal choke coil (i.e., R = 0) is

• a) Zero
• b) Near about zero
• c) Near about one
• d) One

Answer: Zero

Question: At resonance, the value of the power factor in an LCR series circuit is

• a) 1
• b) Zero
• c) Not defined
• d)

  

Answer:  1

Question:

• a) 50
• b) 25
• c) 200
• d) 100

Answer: 50

Question:

• a) Zero
• b)

  

• c)

  

• d)

  

Answer: Zero

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d) None of these

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: The virtual current of 4 A and 50 Hz flows in an AC circuit containing a coil. The power consumed in the coil is 240 W. If the virtual voltage across the coil is 100 V, then its resistance will be

• a)

  

• b)

  

• c)

  

• d) NONE OF THESE

Answer:

Question:

• a) Zero
• b) 40 W
• c) 20 W
• d)

  

Answer: Zero

Question:

• a) Increase by 200%
• b) Decrease by 200%
• c) Increase by 100%
• d) Decrease by 100%

Answer: Increase by 200%

Question: A step-up transformer operates on 220 V line and supplies 2.2 A. The ratio of primary and secondary winding is 11 : 50. The output voltage in the secondary is

• a) 1000 V
• b) 0 V
• c) 100 V
• d) 220 V

Answer: 1000 V

Question:

• a) 0 A, 0 A
• b) 10 A, 0 A
• c) 0 A, 10 A
• d)

  

Answer: 0 A, 0 A

Question: In L-C oscillation, maximum charge on capacitor can be Q. If at any instant, electric energy and magnetic energy associated with circuit is equal, then charge on capacitor at that instant is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c) Zero
• d) R

Answer:

Question:

• a) 30 A
• b)

  

• c)

  

• d)

  

Answer: 30 A

Question:

• a) 2W
• b)

  

• c)

  

• d) W

Answer: 2W

Question:

• a)

  

• b)

  

• c)

  

• d)Both bulbs have equal brightness

Answer: