A coaxial cable is made up of two conductors. The inner conductor is solid is of radius `R_(1)` and the outer coductor is hollow of inner radius `R_(2)` and outer radius `R_(3)` . The space between the conductors are carrying currents of equal magnitudes and in oppsite direactions. then the variation of magnetic field with distance form the axis is best plotted as :

Options

A. `-y-direction`
B. `+z-direction`
C. `-z-`direction
D. `-x-`direction

Answer

B

Explanation

Here, velocity of EM wave, `v=vhat(i)`
Instaneous oscillating electric field,
`E=Ehat(j)`
As we already know that, during the propogation of = EM waves through a medium oscillating electric and magnetic field vectors are mutually perpendicular to each other end to the direction of each other and to the direction of propogation of the wave `(ExxB)`. i.e. `ExxB=v rArr (Ehat(j) xx B = vhat(i)` ............(i)
As we know that from vector algebra,
`hat(j) xx hat(k)= hat(i)`..........(ii) ltbr. Comparing Eqs. (i) and (ii), we get
`B= Bhat(k)`,
Where B (say) be the magnitude of magnetic field.
Thus, we can say that the direction of oscillating magnetic field of the em wave will be along +z direction.