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A coil of self-inductance L is connected...

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

Frequency of the `AC` source is decreased

B

Number of turns in the coil is reduced

C

A capacitance of reactance `X_(C)=X_(L)` is included in the same circuit

D

An iron rod is inserted in the coil

Text Solution

Verified by Experts

The correct Answer is:
D
`Z=sqrt(R^(2)+X_(L)^(2)) =sqrt(R^(2)+(2pifL)^(2))`
`I=V/R, P=I^(2)R, f uarr Luarr Zuarr Idarr Pdarr`
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Knowledge Check

  • A coil of self inductance L is connected in series with a bulb and an A.C. source. Brightness of the bulb decreases when

    A
    Number of turns in the coil is reduced
    B
    A capacitance of reactance `X_(c) = X_(L)` is included in the same circuit
    C
    An iron rod is inserted in the coil
    D
    Frequency of the A.C. source is decresed

  • A coil of copper wire is connected in series with a bulb, a battery and a switch. When the circuit is completed the bulb lights up immediately . The circuit is switched off and a rod of soft iron is placed inside the coil . On completing the circuit again . It is observed that :-

    A
    Bulb is not so bright
    B
    There is a slight deley before bulb lights to its normal brightness
    C
    The bulb is initially bright but gradually becomes dim
    D
    The bulb is bright than before

  • Two identical coils each of self-inductance L , are connected in series and are placed so closed to each other that all the flux from one coil links with the other. The total self-inductance of the system is

    A
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    B
    2L
    C
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    D
    4L

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