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Alternating Current · Question 41

AIPMT 2010 (Prelims)MCQEasy📈 Topic in 38% papers+4−1
1

In the given circuit the readings of voltmeters V1 and V2 are 300 volts each. The readings of the voltmeter V3 and ammeter A are respectively [figure]

  1. 150 V, 2.2 A
  2. 220 V, 2.2 A
  3. 220 V, 2.0 A
  4. 100 V, 2.0 A

Answer

(2) 220 V, 2.2 A

Solution

VL = VC = 300 V and VL, VC are opposite in phase,

The circuit is at resonance and the supply voltage appears fully across R.

V = VR2 + (VL - VC)2 VR = V = 220 V

I = VRR = 220100 = 2.2 A

Answer: (2)

AIPMT 2010 (Prelims)

Keep practising — Alternating Current

2

A 220 volt input is supplied to a transformer. The output circuit draws a current of 2.0 ampere at 440 volts. If the efficiency of the transformer is 80%, the current drawn by the primary windings of the transformer is

  1. 3.6 ampere
  2. 2.8 ampere
  3. 2.5 ampere
  4. 5.0 ampere
AIPMT 2010 (Prelims)
3

Power dissipated in an LCR series circuit connected to an A.C. source of emf is

  1. 2 [R2 + (L - 1C )2 ]R
  2. 2 R2 + (L - 1C )2R
  3. 2 R R2 + (L - 1C )2
  4. 2 R [R2 + (L - 1C )2 ]
AIPMT 2009
4

In an a.c. circuit the e.m.f. ( ) and the current (i) at any instant are given respectively by = E0 sin t, i = I0 sin( t - ) The average power in the circuit over one cycle of a.c. is

  1. E0I02
  2. E0I0
  3. E0I02
  4. E0I02
AIPMT 2008
5

The primary and secondary coils of a transformer have 50 and 1500 turns respectively. If the magnetic flux linked with the primary coil is given by = 0 + 4t, where is in webers, t is time in seconds and 0 is a constant, the output voltage across the secondary coil is

  1. 120 volt
  2. 220 volts
  3. 30 volts
  4. 90 volts
AIPMT 2007
6

A transformer is used to light a 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 amp, the efficiency of the transformer is approximately

  1. 50%
  2. 90%
  3. 10%
  4. 30%
AIPMT 2007
7

What is the value of inductance L for which the current is maximum in a series LCR circuit with C = 10 F and = 1000 s-1 ?

  1. 1 mH
  2. cannot be calculated unless R is known
  3. 10 mH
  4. 100 mH
AIPMT 2007
8

A coil of inductive reactance 31 has a resistance of 8 . It is placed in series with a condenser of capacitative reactance 25 . The combination is connected to an a.c. source of 110 V. The power factor of the circuit is

  1. 0.33
  2. 0.56
  3. 0.64
  4. 0.80
AIPMT 2006
9

The core of a transformer is laminated because

  1. ratio of voltage in primary and secondary may be increased
  2. energy losses due to eddy currents may be minimised
  3. the weight of the transformer may be reduced
  4. rusting of the core may be prevented.
AIPMT 2006
10

A transistor-oscillator using a resonant circuit with an inductor L (of negligible resistance) and a capacitor C in series produces oscillations of frequency f. If L is doubled and C is changed to 4C, the frequency will be

  1. f/2
  2. f/4
  3. 8f
  4. f/2 2
AIPMT 2006
11

In a circuit L, C and R are connected in series with an alternating voltage source of frequency f. The current leads the voltage by 45 . The value of C is

  1. 1 f(2 fL - R)
  2. 12 f(2 fL - R)
  3. 1 f(2 fL + R)
  4. 12 f(2 fL + R)
AIPMT 2005

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