Electromagnetic Waves

Due to presence of an em-wave whose electric component is given by E = 100 ( t - kx) NC-1 a cylinder of length 200 cm holds certain amount of em-energy inside it. If another cylinder of same length but half diameter than previous one holds same amount of em-energy, the magnitude of the electric field of the corresponding em-wave should be modified as

1. 50 ( t - kx) NC-1
2. 400 ( t - kx) NC-1
3. 200 ( t - kx) NC-1
4. 25 ( t - kx) NC-1

The magnetic field of an E.M. wave is given by B = ( 32 i + 12 j )30 [ (t - zc ) ] (S.I. Units). The corresponding electric field in S.I. units is:

1. E = ( 12 i + 32 j )30c [ (t + zc ) ]
2. E = ( 12 i - 32 j )30c [ (t - zc ) ]
3. E = ( 32 i - 12 j )30c [ (t + zc ) ]
4. E = ( 34 i + 14 j )30c [ (t - zc ) ]

Arrange the following in the ascending order of wavelength ( ) : Choose the most appropriate answer from the options given below :

1. 4 < 3 < 2 < 1
2. 4 < 2 < 3 < 1
3. 3 < 4 < 2 < 1
4. 4 < 3 < 1 < 2

The electric field of an electromagnetic wave in free space is E=57 [7.5 106t-5 10-3(3x+4y) ](4 i-3 j) N/C. The associated magnetic field in Tesla is

1. B= 573 108 [7.5 106t-5 10-3(3x+4y) ]( k)
2. B= 573 108 [7.5 106t-5 10-3(3x+4y) ](5 k)
3. B=- 573 108 [7.5 106t-5 10-3(3x+4y) ]( k)
4. B=- 573 108 [7.5 106t-5 10-3(3x+4y) ](5 k)

A plane electromagnetic wave of frequency 20 MHz travels in free space along the +x direction. At a particular point in space and time, the electric field vector of the wave is Ey=9.3 V m-1. Then, the magnetic field vector of the wave at that point is

1. Bz=1.55 10-8 T
2. Bz=6.2 10-8 T
3. Bz=3.1 10-8 T
4. Bz=9.3 10-8 T

A time varying potential difference is applied between the plates of a parallel plate capacitor of capacitance 2.5 . The dielectric constant of the medium between the capacitor plates is 1 . It produces an instantaneous displacement current of 0.25 mA in the intervening space between the capacitor plates, the magnitude of the rate of change of the potential difference will be V s-1.

A parallel plate capacitor of area A=16 cm2 and separation between the plates 10 cm , is charged by a DC current. Consider a hypothetical plane surface of area A0=3.2 cm2 inside the capacitor and parallel to the plates. At an instant, the current through the circuit is 6A. At the same instant the displacement current through A0 is mA .