**NEET AIPMT Physics Chapter Wise Solutions – Electromagnetic Induction and Alternating Current**

Contents

NEET AIPMT Physics Chapter Wise SolutionsChemistryBiology

**1. A series R-C circuit is connected to an alternating voltage source. Consider two situations (AIPMT 2015)**

(a) When capacitor is air filled.

(b) When capacitor is mica filled.

Current through resistor is i and voltage across capacitor is V then

**2. An electron moves on a straight line path XY as shown. The abed is a coil adjacent to the path of electron. What will be the direction of current, if any, induced in the coil? (AIPMT 2015)**

**3. A resistance ‘R’ draws power ‘P’ when conBected to an AC source. If an inductance is now placed in series with the resistance, such that the impedance of the circuit becomes “Z” the power drawn will be (AIPMT 2015, Cancelled)**

**4. A thin semicircular conducting ring (PQR) of radius r is falling with its plane vertical in a horizontal magnetic field B, as shown in the figure.**

**The potential difference developed across the ring when its speed is v, is (AIPMT 2014)**

**5. A transformer having efficiency of 90% is working on 200 V and 3 kW power supply. If the current in the secondary coil is 6 A, the voltage across the secondary coil and the current in the primary coil respectively are (AIPMT 2014)**

(a) 300 V, 15 A

(b) 450 V, 15 A

(c) 450 V, 13.5 A

(d) 600 V, 15 A

**6. A wire loop is rotated in a magnetic field. The frequency of change of direction of the induced e.m.f. is (NEET 2013)**

(a) four times per revolution

(b) six times per revolution

(c) once per revolution

(d) twice per revolution

**7. A coil of self-inductance L is connected in series with a bulb B and an AC source. Brightness of the bulb decreases when (NEET 2013)**

(a) a capacitance of reactance X_{c} = X_{L} is included in the same circuit.

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

(c) frequency of the AC source is decreased.

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

**8. The primary of a transformer when connected to a dc battery of 10 Volt draws a current of 1 mA. The number of turns of the primary and secondary windings are 50 and 100 respectively. The voltage in the secondary and the current drawn by the cricuit in the secondary are respectively(Karnataka NEET 2013)**

(a) 20 V and 2.0 mA

(b) 10 V and 0.5 mA

(c) Zero volt and therefore no current

(d) 20 V and 0.5 mA

**9. A current of 2.5 A flows through a coil of inductance 5 H. The magnetic flux linked with the coil is (Karnataka NEET 2013)**

(a) 0.5 Wb

(b) 12.5 Wb

(c) zero

(d) 2 Wb

**10. A coil of resistance 400 Ω is placed in a magnetic field. If the magnetic flux Φ (Wb) linked with the coil varies with time t (sec) as Φ = 50T ^{2} + 4. The current in the coil at t = 2 sec is (Prelims 2012)**

(a) 0.5 A

(b) 0.1 A

(c) 2 A

(d) 1 A

**11. In an electrical circuit R, L, C and ac voltage source are all connected in series. When L is removed from the circuit, the phase difference between the voltage and the current in the circuit is If instead, C is removed from the circuit, the phase difference is again The power factor of the circuit is (Prelims 2012)**

**12. The current (I) in the inductance is varying with time according to the plot shown in figure. (Prelims 2012)**

**Which one of the following is the correct variation of voltage with time in the coil?**

**13. The instantaneous values of alternating current and voltages in a circuit are given as (mains 2012)**

**14. In a coil of resistance 10 Q, the induced current developed by changing magnetic flux through it, is shown in figure as a function of time. The magnitude of change in flux through the coil in weber is (Mains 2012)**

(a) 8

(b) 2

(c) 6

(d) 4

**15. An ac voltage is applied to a resistance R and an inductor L in series. If R and the inductive reactance are both equal to 3 Ω, the phase difference between the applied voltage and the current in the circuit is (Prelims 2011)**

(a) π/6

(b) π/4

(c) π /2

(d) zero

**16. In an ac circuit an alternating voyage volts is connected to a capacitor of capacity 1 µF. The r.m.s. value of the current in the circuit is (Prelims 2011)**

(a) 10 mA

(b) 100 mA

(c) 200 mA

(d) 20 mA

**17. The current i in a coil varies with time as shown in the figure. The variation of induced emf with time would be (prelims 2011)**

**18. The r.m.s. value of potential difference V shown in the figure is (mains 2011)**

**19. A coil has resistance 30 ohm and inductive reactance 20 ohm at 50 Hz frequency. If an ac source, of 200 volt, 100 Hz, is connected across the coil, the current in the coil will be (mains 2011)**

**20. A conducting circular loop is placed in a uniform magnetic field, B = 0.025 T with its plane perpen-dicular to the loop. The radius of the loop is made to shrink at a constant rate of 1 mm s ^{-1}. The induced emf when the radius is 2 cm, is (Prelims 2010)**

(a) 2 π µ V

(b) π µV

(c) π/2 µ V

(d) 2 µ V

**21. In the given circuit the reading of voltmeter v _{1} and v_{2} are 300 volts each. The reading of the voltmeter v_{3} and ammeter A are respectively (prelims 2010)**

(a) 150V,2.2A

(b) 220V,2.2A

(c) 220V,2.0A

(d) 100V,2.0A

**22. 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 (Prelims 2010)**

(a) 3.6 ampere

(b) 2.8 ampere

(c) 2.5 ampere

(d) 5.0 ampere

**23. A condenser of capacity C is charged to a potential difference of v _{1} The plates of the condenser are then connected to an ideal inductor of inductance L. The current through the inductor when the potential difference across the condenser reduces to v_{2 }is (mains 2010)**

**24. A rectangular, a square, a circular and an elliptical loop, all in the (x-y) plane, are moving out of a uniform magnetic field with a constant velocity, (Prelims 2009)**

V = vi. The magnetic field is directed along the negative z axis direction. The induced emf, during the passage of these loops, out of the field region, will not remain constant for

(a) the circular and the elliptical loops

(b) only the elliptical loop

(c) any of the four loops

(d) the rectangular, circular and elliptical loops

**25. Power dissipated in an LCR series circuit connected to an A.C. source of emf e is (prelims 2009)**

**26. A conducting circular loop is placed in a uniform magnetic field 0.04 T with its plane perpendicular to the magnetic field. The radius of the loon starts shrinking at 2 mm/s. The induced emf in the loop when the radius is 2 cm is (2009 prelims)**

(a) 4.8 π µ V

(b) 0.8 π µ V

(c) 1.6 π µ V

(d) 3.2 π µ V

**27. A long solenoid has 500 turns. When a current of 2 ampere is passed through it, the resulting magnetic flux linked with each turn of the solenoid is 4 × 10 ^{-3} Wb. The self-inductance of the solenoid is (Prelims 2008)**

(a) 1.0 henry

(b) 4.0 henry

(c) 2.5 henry

(d) 2.0 henry

**28. In an a.c. circuit the e.m.f. () and the current (i) at any instant arc given respectively by**

**29. A circular disc of radius 0.2 meter is placed in a uniform magnetic field of induction 1 / π (wb/m ^{2}) in such a way that its axis makes an angle of 60° with (prelims 2008)**

**30. The primary and secondary coils of a transformer have 50 and 1 500 turns respectively. If the magnetic flux Φ linked with the primary coil is given by Φ = Φ _{0} + 4t where Φ is in webers, t is time in seconds and Φ_{0} is a constant, the output voltage across the secondary coil is (2007)**

(a) 120 volts

(b) 220 volts

(e) 30 volts

(d) 90 volts.

**31. 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 (2007)**

(a) 50%

(b) 90%

(c) 10%

(d) 30%.

**32. What is the value of inductance L for which the current is maximum in a series LCR circuit with C= 10 µF andco= 1000 S ^{-1}? (2007)**

(a) 1 mH

(b) cannot be.calculated unless R is known

(c) 10 mH

(d) 100 mH.

**33. A coil of inductive reactance 31 Ω has a resistance of 8 Ω. It is placed in series with a condenser of capacitative reactance 25 Ω. The combination is connected to an a.c. source of 110 V. The power factor of the circuit is (2006)**

(a) 0.33

(b) 0.56

(c) 0.64

(d) 0.80

**34. Two coils of self inductance 2 mH and 8 mH are placed so close together that the effective flux in one coil is completely linked with the other. The mutual inductance between these coils is (2006)**

(a) 16 mH

(b) 10 mH

(c) 6 mH

(d) 4 mH.

**35. The core of a transformer is laminated because (2006)**

(a) ratio of voltage in primary and secondary may be increased

(b) energy losses due to eddy currents may be minimised

(c) the weight of the transformer may be reduced

(d) rusting of the core may be prevented.

**36. A transistor-oscillator using a resonant circuit with an inductor L (of negligible resistance) and a capacitor C in series produce oscillations of frequency l If L is doubled and C is changed to 4C, the frequency will be (2006)**

**37. 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 (2005)**

**38. As a result of change in the magnetic flux linked to the closed loop as shown in the figure, an e.m.f V volt is induced in the loop. ****The work done (joule) in taking a charge 0 coulomb once along the loop is (2005)**

(a) QV

(b) 2QV

(c) QV/ 2

(d) zero.

**39. A coil of 40 henry inductance is connected in series with a resistance of 8 ohm and the combination is joined to the terminals of a 2 volt battery. The time constant of the circuit is (2004)**

(a) 5 seconds

(b) 1/5 seconds

(c) 40 seconds

(d) 20 seconds

**40. The magnetic flux through a circuit of resistance R changes by an amount ΔΦ in a time Δt. Then the total quantity of electric charge 0 that passes any point in the circuit during the time Δt is represented by (2004)**

**41. For a series LCR circuit the power loss at resonance is (2002)**

**42. For a coil having L = 2 mH, current flow through it is l = t ^{2} e^{-1 }then, the time at which emf become zero \ (2001)**

(a) 2 sec

(b) 1 sec

(c) 4 sec

(d) 3 sec.

**43. A capacitor of capacity C has reactance X. If capacitance and frequency become double then reactance will be (2001)**

(a) 4X

(b) X/ 2

(c) X/4

(d) 2X.

**44. The value of quality factor is (2000)**

**45. In the circuit given in figure, 1 and 2 are ammeters. Just after key K is pressed to complete the circuit, the reading will be (1999)**

(a) zero in 1, maximum in 2

(b) maximum in both 1 and 2

(c) zero in both 1 and 2

(d) maximum in 1, zero in 2

**46. A step-up transformer operates on a 230 V line and supplies a load of 2 ampere. The ratio of the primary and secondary windings is ****1 : 25. The current in the primary is (1998)**

(a) 15 A

(b) 50 A

(c) 25 A

(d) 12.5 A

**47. Two coils have a mutual inductance 0.005 H. The current changes in the first coil according to equation i = i _{0} sin cot, where i_{0} = 10 A and co = 100 π rad/sec. The maximum value ofe.m.f. in the second coil is (1998)**

(a)

**π**

(b) 5

**π**

(c) 2

**π**

(d) 4

**π**

**48. The primary winding of a transformer has 500 turns whereas its secondary has 5000 turns. The primary is connected to an A.C. supply 20 V, 50 Hz. The secondary will have an output of (1997)**

(a) 2 V, 50 Hz

(b) 2 V, 5 Hz

(c) 200 V, 50 Hz

(d) 200 V, 500 Hz.

**49. In an a.c. circuit with phase voltage V and current 7, the power dissipated is**

**50. A metal ring is held horizontally and bar magnet is dropped through the ring with its length along the axis of the ring. The acceleration of the falling magnet is (1996)**

(a) more than g

(b) equal to g

(c) less than g

(d) either (a) or (c).

**51. In an A.C. circuit, the current flowing is 7=5 sin (1007 – TC/2) ampere and the potential difference is V = 200 sin (1007) volts. The power consumption is equal to * (1995)**

(a) 20 W

(b) 0 W

(c) 1000 W

(d) 40 W.

**52. When the key K is pressed at time t = 0, then which of the following statement about the current 7 in the resistor AB of the given circuit is true?**

(a) I oscillates between 1 mA and 2 mA

(b) at t = 0, I=2 mA and with time it goes to imA

(c) i = ImA at all t

(d) i =2 mA at all t.

**53. A straight line conductor of length 0.4 m is moved with a speed of 7 m/s perpendicular to a magnetic field of intensity 0.9 Wb/m ^{2}. The induced e.m.f. across the conductor is (1995)**

(a) 5.04 V

(b) 25.2 V

(c) 1.26 V

(d) 2.52 V.

**54. The current 7 in an A.C. circuit inductance coil varies with time according to the graph given below.**

** **

**Which one of the following graphs gives the variation of voltage with time ? (1994)**

**55. In an A.C. circuit, 7nns and 70 are related as (1994)**

**56. An series L-C-R circuit is connected to a source of A.C. current. At resonance, the phase difference between the applied voltage and the current in the circuit, is (1994)**

**57. Two cables of copper are of equal lengths. One of them has a single wire of area of cross-section A, while other has 10 wires of cross-sectional area .4/10 each. Give their suitability for transporting A.C. and D.C. (1994)**

(a) only multiple strands for A.C., either for D.C.

(b) only multiple strands for A.C., only single strand for D.C.

(c) only single strand for D.C., either for A.C.

(d) only single strand for A.C., either for D.C.

**58. If N is the number of turns in a coil, the value of self inductance varies as (1993)**

(a) N^{0}

(b) N

(c) N^{2}

(d) N^{-2}

**59. What is the self-inductance of a coil which produces 5 mV when the current changes from 3 ampere to 2 ampere in one millisecond? (1993)**

(a) 5000 henry

(b) 5 mili-henry

(c) 50 henry

(d) 5 henry

**60. The time constant of C-R circuit is (1992)**

(a) 1 /CR

(b) C/R

(c) CR

(d) R/C

**61. The total charge, induced in a conducting loop when it is moved in magnetic field depend on (1992)**

(a) the rate of change of magnetic flux

(b) initial magnetic flux only

(c) the total change in magnetic flux

(d) final magnetic flux only

**62. A rectangular coil of 20 turns and area of cross-section 25 sq. cm has a resistance of 100 Ω. If a magnetic field which is perpendicular to the plane of coil changes at a rate of 1000 tesla per second, the current in the coil is (1992)**

(a) 1A

(b) 50 A

(c) 0.5 A

(d) 5 A

**63. Faraday’s laws are consequence of conservation of (1991)**

(a) energy

(b) energy and magnetic field

(c) charge

(d) magnetic field

**64. If the number of turns per unit length of a coil of solenoid is doubled, the self-inductance of the solenoid will (1991)**

(a) remain unchanged

(b) be halved

(c) be doubled

(d) become four times

**65. A 100 millihenry coil carries a current of 1 A. Energy stored in its magnetic field is (1991)**

(a) 0.5 J

(b) 1A

(c) 0.05 J

(d) 0.1 J

**66. A magnetic field of 2 × 10 ^{-2} T acts at right angles to a coil of area 100 cm^{2}, with 50 turns. The average e.m.f. induced in the coil is 0.1 V, when it is removed from the field in t sec. The value of t is (1991)**

(a) 10 s

(b) 0.1 s

(c) 0.01 s

(d) 1 s

**67. The current in self inductance L = 40 mH is to be increased uniformly from 1 amp to 11 amp in 4 milliseconds. The e.m.f. induced in inductor during process is (1990)**

(a) 100 volt

(b) 0.4 volt

(c) 4.0 volt

(d) 440 volt

**68. An inductor may store energy in (1990)**

(a) its electric field

(b) its coils

(c) its magnetic field

(d) both in electric and magnetic fields

**69. In a region of magnetic induction B = 10 ^{-2} tesla, a circular coil of radius 30 cm and resistance π^{2} ohm is rotated about an axis which is perpendicular to the direction of B and which forms a diameter of the coil. If the coil rotates at 200 rpm the amplitude of the alternating current induced in the coil is (1988)**

(a) 4 π

^{2 }mA

(b) 30 mA

(c) 6 mA

(d) 200 mA

**70. Eddy currents are produced when (1988)**

(a) a metal is kept in varying magnetic field

(b) a metal is kept in steady magnetic field

(c) a circular coil is placed in a magnetic field

(d) through a circular coil, current is passed

**EXPLANATIONS**

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