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When an electromagnetic waves enter the ...

When an electromagnetic waves enter the ionised layer of ionosphare, the motion of electron cloud produces a spece current and the electric field has its own capacitative displacement current , then

A

the space current is in phase of displacement current

B

the space current lags behind the displacement current by a phase `180^(@)`.

C

the space current lags behind the displacement current by a phase `90^(@)`.

D

the space current leads the displacement current by phase `90^(@)`

Text Solution

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The correct Answer is:
A
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Explore conceptually related problems

Read the following passage and then answer questions (a) to (d) on the basis of your under- standing of the passage and the related studied concepts. We are familiar with Ampere.s circuital law which states that for an open surface with a boundary around a current the line integral of magnetic field around the entire boundary of an open surface is equal to mu_(0) times the total current passing through the surface i.e. ointvecB.vec(dl)=mu_(0)I Later on, Maxwell showed that for logical consistency, a changing electric field must also produce a magnetic field. In this context Maxwell introduced the concept of a displacement current given as per relation I_(D)=in_(0)(dphi_(E))/(dt) Thus, as per generalisation made by Maxwell, the source of a magnetic field is not just the conduction electric current due to following charges but also the time rate of change of electric field. In this way, Maxwell modified Ampere.s circuital law and in its modified the law is expressed as: ointvecB.vec(dl)=mu_(0)[I_(C )+I_(D)]=mu_(0)[I_(C )+in_(0)(dphi_(E))/(dt)] In all respects, the displacement current has the same physical effects as the conduction current. It is observed that in same cases, e.g., steady electric field in a wire, displacement current may be zero. In other cases, e.g., a capacitor being charged, both conduction and displacement currents may be present in different regions of space. In most of the cases, conduction current and displacement current may be present simultaneously in the same region of space because there exist no perfectly conducting or perfectly insulating medium. Moreover, there may be large regions of space where there is no conduction current but there is only a displacement current due to time varying electric field. Does displacement current need a conductor to flow.

Read the following passage and then answer questions (a) to (d) on the basis of your under- standing of the passage and the related studied concepts. We are familiar with Ampere.s circuital law which states that for an open surface with a boundary around a current the line integral of magnetic field around the entire boundary of an open surface is equal to mu_(0) times the total current passing through the surface i.e. ointvecB.vec(dl)=mu_(0)I Later on, Maxwell showed that for logical consistency, a changing electric field must also produce a magnetic field. In this context Maxwell introduced the concept of a displacement current given as per relation I_(D)=in_(0)(dphi_(E))/(dt) Thus, as per generalisation made by Maxwell, the source of a magnetic field is not just the conduction electric current due to following charges but also the time rate of change of electric field. In this way, Maxwell modified Ampere.s circuital law and in its modified the law is expressed as: ointvecB.vec(dl)=mu_(0)[I_(C )+I_(D)]=mu_(0)[I_(C )+in_(0)(dphi_(E))/(dt)] In all respects, the displacement current has the same physical effects as the conduction current. It is observed that in same cases, e.g., steady electric field in a wire, displacement current may be zero. In other cases, e.g., a capacitor being charged, both conduction and displacement currents may be present in different regions of space. In most of the cases, conduction current and displacement current may be present simultaneously in the same region of space because there exist no perfectly conducting or perfectly insulating medium. Moreover, there may be large regions of space where there is no conduction current but there is only a displacement current due to time varying electric field. Define displacement current.

Knowledge Check

  • When an electromagnetic wave enters the ionised layer of ionosphere, the motion of electron cloud produces a space current and the electric field has its own capacitative displacement current then.

    A
    The space current is in phase with displacement current.
    B
    The space current lags behind the displacement current by a phase of `180^(@)` .
    C
    the space current lages behind the displacement current by a phase of `90^(@)` .
    D
    the space current leads the displacement current by a phase of `90^(@)` .

  • When electromagnetic waves enter the ionised layer of ionosphere, then the relative permittivity i.e. dielectric constant of the ionised layer

    A
    does not change
    B
    appears to increase
    C
    appears to decrease
    D
    sometimes appears to increase and sometimes to decrease

  • When an electric current is passing through a conductor, there is no electric field produced because the conductor is

    A
    positively charged
    B
    negatively charged
    C
    electrically neutral
    D
    none of these

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