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In a radio receiver, the short wave and ...

In a radio receiver, the short wave and medium wave station are tuned by using the same capacitor but coils of different inductance `L_(s)` and `L_(m)` respectively then

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The value of inductance is more while tuning a radio receiver at midium wave station than that at short wave station. We know that the short wave station emit radiowaves of short wavelength `(lambda_(s))` and medium wave station emit rediowaves of longer wavelength `(lambda_(m))`, i.e.,
`lambda_(m)gtlambda_(s)`.
Let `v_(s),v_(m)` be the frequencies of short wave and medium wave signals.
Then `v_(s)=c//lambda_(s)` and `v_(m)=c//lambda_(m)`
or `v_(s)/v_(m)=lambda_(m)/lambda_(s)` .....(i)
If `L_(s),L_(m)` be the self inductance of the short wave and the medium wave coils respectively and C be the capacitance of capacitor used, then
`v_(s)=(1)/(2pisqrt(L_(s)C))` and `v_(m)=(1)/(2pisqrt(L_(m)C))`
`:. v_(s)/v_(m)=sqrt(L_(m)/L_(s))` or `v_(s)^(2)/v_(m)^(2)=L_(m)/L_(s)` ...(ii)
From (i) and (ii),
`L_(m)/L_(s)=(lambda_(m^(2)))/(lambda_(s^(2)))gt 1 (As lambda_(m)gtlambda_(s)) :. L_(m) gt L_(s)`
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Knowledge Check

  • In a radio receiver, the short wave and medium wave station are tuned by using the same capacitoer butcoils of different inductance L_(s) and L_(m) respectively then

    A
    `L_(s)gtL_(m)`
    B
    `L_(s)ltL_(m)`
    C
    `L_(s)=L_(m)`
    D
    None of these
  • Long distance short - wave radio brad - casting uses

    A
    ground wave
    B
    ionospheric wave
    C
    direct wave
    D
    sky wave
  • Two different coils have self-inductance L_(1)=8 mH, L_(2)=2 mH . The current in one coil is increased at a constant rate. The current in the second coil is also increased at the same rate. At a certain instant of time, the power given to the two coils is the same. At that time the current, the induced voltage and the energy stored in the first coil are i_(1), V_(1) and W_(1) respectively. Corresponding values for the second coil at the same instant are i_(2), V_(2) and W_(2) respectively. Then

    A
    `(i_(1))/(i_(2))=(1)/(4)`
    B
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    C
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    D
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