Electromagnetic Waves

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 .

A plane EM wave is propagating along x direction. It has a wavelength of 4 mm. If electric field is in y direction with the maximum magnitude of 60 V m-1, the equation for magnetic field is :

1. Bz = 2 10-7 [ 2 (x - 3 108 t ) ] k T
2. Bz = 2 10-7 [ 2 103 (x - 3 108 t ) ] k T
3. Bz = 60 [ 2 (x - 3 108 t ) ] k T
4. Bx = 60 [ 2 (x - 3 108 t ) ] i T

The magnetic field in a plane electromagnetic wave is By = (3.5 10-7 ) (1.5 103 x + 0.5 1011 t ) T. The corresponding electric field will be :

1. Ez = 105 (1.5 103 x + 0.5 1011 t ) V m-1
2. Ey = 10.5 (1.5 103 x + 0.5 1011 t ) V m-1
3. Ey = 1.17 (1.5 103 x + 0.5 1011 t ) V m-1
4. Ez = 1.17 (1.5 103 x + 0.5 1011 t ) V m-1

Average force exerted on a non-reflecting surface at normal incidence is 2.4 10-4 N. If 360 W/cm2 is the light energy flux during span of 1 hour 30 minutes, then the area of the surface is:

1. 20 m2
2. 0.2 m2
3. 0.1 m2
4. 0.02 m2

Electromagnetic waves travel in a medium with speed of 1.5 108 m s-1. The relative permeability of the medium is 2.0. The relative permittivity will be:

1. 4
2. 1
3. 2
4. 5

In the given electromagnetic wave Ey = 600 ( t - kx) Vm-1, intensity of the associated light beam is (in W/m2) : (Given 0 = 9 10-12 C2 N-1 m-2)

1. 486
2. 729
3. 243
4. 972

An alternating voltage of amplitude 40 V and frequency 4 kHz is applied directly across the capacitor of 12 . The maximum displacement current between the plates of the capacitor is nearly :

1. 10 A
2. 8 A
3. 13 A
4. 12 A

Match List I with List II : Choose the correct answer from the options given below :

1. (A)-(I), (B)-(III), (C)-(II), (D)-(IV)
2. (A)-(III), (B)-(II), (C)-(IV), (D)-(I)
3. (A)-(IV), (B)-(III), (C)-(II), (D)-(I)
4. (A)-(II), (B)-(I), (C)-(IV), (D)-(III)

The electric field in an electromagnetic wave is given by E= i40 (t-z/c) NC-1. The magnetic field induction of this wave is (in SI unit) :

1. B= j 40c (t-z/c)
2. B= i 40c (t-z/c)
3. B= j40 (t-z/c)
4. B= k 40c (t-z/c)