Question 1

A parallel plate capacitor consists of two circular plates of radius R=0.1 ~m . They are separated by a short distance. If electric field between the capacitor plates changes as d E d t =6 10^ 13 ~V ~

Accepted Answer

Given, area of plates, A= R^2=3.14 (0.1)^2 ~m ^2 and d E d t =6 10^ 13 ~V ~m s Displacement current between the plates, aligned I_d & = _0 d d t \ I_d & = _0 A ( d E d t ) [ d d t =A d E d t ] \ & =8.85 10^ -12 3.14 (0.1)^2 6 10^ 13 \ I_d & =16.67 ~A aligned

Question 2

Electromagnetic waves travel in a medium with speed of 1.5 10^8 ~ms ^ -1 . The relative permeability of the medium is 2.0 . The relative permittivity will be :

Accepted Answer

v= C _ r _ r 1.5 10^8= 3 10^8 2 _ r 2 _ T =4 _ T =2

Question 3

If E and K represent electric field and propagation vectors of the EM waves in vacuum, then magnetic field vector is given by: ( - angular frequency) :

Accepted Answer

For an EM wave B = 1 ( K E )

Question 4

Which of the following Maxwell's equations is valid for time varying conditions but not valid for static conditions :

Accepted Answer

For time varying condition Maxwell's equation, E dl =- d _ B dt

Question 5

The ratio of average electric energy density and total average energy density of electromagnetic wave is :

Accepted Answer

We have U _ E U _ T = U _ E U _ E + U _ B = U _ E 2 U _ E = 1 2 [ U _ E = U _ B = 1 2 _0 E _0^2= B _0^2 2 _0 ]

Question 6

An electromagnetic wave is propagating along X-axis. At x=1 ~cm and t=18 ~s , its electric vector |E|=8 ~V / m , then the magnitude of its magnetic vector is

Accepted Answer

As we know that, E B =c so, B= E c = 8 3 10^8 =2.66 10^ -8

Electromagnetic Waves — Previous Year Questions & Solutions