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1. 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 in seconds is

A. 5 B. 20 C. 0.2 D. 50

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2. For a series LCR circuit, the power loss at resonance is

A. zero B. minimum C. maximum D. infinite

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3. A capacitor of capacity C has reactance X. If capacitance and frequency become double then reactance will be

A. X B. X/2 C. X/4 D. 2X

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4. The value of quality factor is

A. R/L B. R/C C. 1/RC D. 1/RL

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5. A 100 millihenry coil carries a current of 1A. Energy stored in its magnetic field is

A. 0.5 J B. 1 A C. 0.05 J D. 0.1 J

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6. If the number of turns per unit length of a coil of solenoid is doubled, the self-inductance of the solenoid will

A. remain unchanged B. be halved C. be doubled D. become four times

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7. A rectangular coil of 20 turns and area of cross-section 25 sq. cm has a resistance of 100Ω. 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

A. 1 A B. 50 A C. 0.5 A D. 5 A

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8. The total charge induced in a conducting loop when it is moved in a magnetic field depends on

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

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9. What is the self-inductance of a coil which produces 5V when the current changes from 3 ampere to 2 ampere in one millisecond?

A. 5000 henry B. 5 milli-henry C. 50 henry D. 5 henry

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10. If N is the number of turns in a coil, the value of self inductance varies as

A. N^0 B. N C. N^2 D. N^-2

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11. A conductor of length 0.4 m is moving with a speed of 7 m/s perpendicular to a magnetic field of intensity 0.9 Wb/m². The induced e.m.f. across the conductor is

A. 1.26 V B. 2.52 V C. 5.04 V D. 25.2 V

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12. A varying current in a coil changes from 10A to zero in 0.5 sec. If the average e.m.f induced in the coil is 220V, the self-inductance of the coil is

A. 5 H B. 6 H C. 11 H D. 12 H

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13. Two coils have a mutual inductance 0.005 H. The current changes in the first coil according to equation I = I₀ sin ωt, where I₀ = 10A and ω = 100π radian/sec. The maximum value of e.m.f. in the second coil is

A. 2π B. 5π C. π D. 4π

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14. In an inductor of self-inductance L = 2 mH, current changes with time according to relation i = t² e^(-t). At what time emf is zero?

A. 4s B. 3s C. 2s D. 1s

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15. 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 Q that passes any point in the circuit during the time Δt is represented by

A. Δφ/R B. R/Δφ C. ΔφΔt/R D. RΔt/Δφ

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16. As a result of change in the magnetic flux linked to the closed loop, an e.m.f. V volt is induced in the loop. The work done (joules) in taking a charge Q coulomb once along the loop is

A. QV B. 2QV C. QV/2 D. Zero

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17. Two coils of self-inductances 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

A. 6 mH B. 4 mH C. 16 mH D. 10 mH

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18. 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

A. 2.5 henry B. 2.0 henry C. 1.0 henry D. 40 henry

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19. 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. 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

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20. An inductor of inductance L, a capacitor of capacitance C, and a resistor of resistance R are connected in series to an AC source of potential difference V volts as shown in the figure. Potential difference across L, C, and R is 40 V, 10 V, and 40V, respectively. The amplitude of the current flowing through the LCR series circuit is 10√2A. The impedance of the circuit is:

A. 4Ω B. 5Ω C. 4√2Ω D. 5√2Ω