Displacement Current & Maxwell's Equations — Practice Questions

Free NEET Physics multiple-choice questions on Displacement Current & Maxwell's Equations. Attempt each question and reveal the answer with a full explanation.

If the amplitude of the magnetic field of an electromagnetic wave is 510 nT , what is the amplitude of the electric field? 153 V/m 1.7 10 -15 V/m 510 V/m 1.53 10 2 V/m In a capacitor being charged by a DC source, the displacement current I d is non-zero: Only while the charge on the plates is changing At all times, even after the capacitor is fully charged Only when the capacitor is fully charged Only if the dielectric is a perfect conductor The average intensity of a plane electromagnetic wave with electric field amplitude E 0 is: 1 2 0 c E 0 2 0 c E 0 2 1 2 E 0 2 μ 0 c E 0 2 μ 0 c If the peak value of the magnetic field in an EM wave is 2 × 10 -7 T , what is the peak value of the electric field? 60 V/m 0.66 × 10 -15 V/m 2 × 10 8 V/m 3 × 10 8 V/m The electric field in a plane electromagnetic wave is given by E y = 400 sin (10 7 t - kx) . The magnetic field amplitude is: 1.33 × 10 -6 T 400 T 1.2 × 10 11 T 1.33 × 10 -7 T If 0 and μ 0 are the permittivity and permeability of vacuum and and μ are those of a medium, then the refractive index n of the medium is: √ μ μ 0 0 √ μ 0 0 μ μ μ 0 0 μ 0 0 μ The oscillating magnetic field in a plane electromagnetic wave is given by B y = 8 10 -6 sin [2 10 11 t + 300 x ] T . Calculate the peak value of the electric field. 2400 V/m 1200 V/m 800 V/m 400 V/m The magnetic field in a plane electromagnetic wave is given by B y = 2 10 -7 sin (0.5 10 3 x + 1.5 10 11 t) T . This electromagnetic wave is: Visible light Infrared Microwaves Radio waves The displacement current is the same as the conduction current when the source is: An AC source A DC source at steady state A transient DC source only Never the same The ratio of contributions made by the electric field and magnetic field components to the intensity of an electromagnetic wave is: 1 : 1 c : 1 c 2 : 1 0 : 0 The Poynting vector S represents the power per unit area and is given by: 1 0 ( E B ) 0 ( E B ) E B E B In an EM wave, the average energy density associated with the magnetic field is: B rms 2 / (2 0) B 0 2 / (2 0) B 0 2 / (4 0) B rms 2 / 0 The magnetic field in a plane electromagnetic wave is given by B = (2 10 -7 ) (0.5 10 3 x + 1.5 10 11 t) j . The wave is travelling along: Negative x-direction Positive x-direction Positive y-direction Negative z-direction The electric field of an EM wave in vacuum is E = 3.1 N/C cos [1.8 rad/m y + 5.4 10 8 rad/s t] . The wavelength of this wave is: 3.5 m 1.8 m 1.1 m 5.4 m If the relative permittivity and relative permeability of a medium are 2.25 and 1.0 respectively, the speed of EM waves in the medium is: 2 10 8 m/s 3 10 8 m/s 2.25 10 8 m/s 1.5 10 8 m/s The electric field of a plane electromagnetic wave is given by E = E 0 ( t - kx) . Which of the following expressions represents the displacement current density ( J d ) in free space? 0 E 0 ( t - kx) 0 E 0 ( t - kx) 0 E 0 ( t - kx) 0 0 E 0 ( t - kx) The intrinsic impedance of free space, defined as the ratio of the amplitudes of the electric field to the magnetic field ( E 0/H 0 ), has the value of approximately: 377 120 3 10 8 50 The energy of an electromagnetic wave is distributed between the electric field and the magnetic field. In a medium with refractive index n , the ratio of electric energy density ( u E ) to magnetic energy density ( u B ) is: 1:1 n:1 n 2:1 1:n 2 In a plane electromagnetic wave, which of the following is correct regarding the phase relationship of E and B ? Both E and B reach their maximum and minimum values at the same time and place E reaches maximum when B is zero E lags behind B by /2 B lags behind E by /2 The speed of electromagnetic waves in a medium is 2 10 8 m/s . If the relative permeability of the medium is 1 , find the relative permittivity. 2.25 1.5 4.5 9 For an electromagnetic wave propagating in a medium, the magnetic field amplitude is B 0 = 5 10 -7 T and the electric field amplitude is E 0 = 100 V/m . The speed of the wave in this medium is: 2 10 8 m/s 3 10 8 m/s 1.5 10 8 m/s 5 10 7 m/s The electric field of an EM wave is given by E = E 0 i (kz + t) . The direction of propagation is: Negative z -direction Positive z -direction Positive x -direction Negative x -direction What is the peak energy density of an electromagnetic wave whose electric field peak value is E 0 ? 0 E 0 2 1 2 0 E 0 2 1 4 0 E 0 2 2 0 E 0 2 Which scientist was the first to demonstrate that electromagnetic waves can be produced in a laboratory using a spark-gap transmitter? Heinrich Hertz James Clerk Maxwell Guglielmo Marconi Jagadish Chandra Bose In an EM wave, the amplitude of the electric field is E 0 and that of the magnetic field is B 0 . The energy density of the wave is: 1 2 0 E 0 2 0 E 0 2 1 2 B 0 2 0 1 2 ( 0 E 0 2 + B 0 2 0 ) A plane electromagnetic wave of frequency 25 MHz travels in free space along the x -direction. At a particular point in space and time, the electric field is E = 6.3 j V/m . What is the magnetic field B at this point? 2.1 10 -8 k T 2.1 10 -8 j T 1.89 10 9 k T 6.3 10 -8 k T The ratio of the magnitude of the magnetic field to the magnitude of the electric field ( B/E ) for an electromagnetic wave in a medium of refractive index n is: n/c 1/c c/n nc In an electromagnetic wave, the electric field oscillates sinusoidally with an amplitude of 48 V/m . The RMS value of the oscillating magnetic field is: 1.1 10 -7 T 1.6 10 -7 T 2.4 10 -7 T 4.8 10 -7 T The average energy density of an electromagnetic wave can be expressed in terms of the RMS electric field ( E rms ) as: 0 E rms 2 1 2 0 E rms 2 2 0 E rms 2 0 E 0 2 The oscillating electric field of an electromagnetic wave is given by E y = 30 (2 10 11 t + 300x) V/m . The wavelength of this wave is: 2.1 10 -2 m 1.5 10 -2 m 4.2 10 -2 m 3.0 10 -2 m An electromagnetic wave has an energy density u . If the speed of the wave is c , the radiation pressure exerted on a perfectly absorbing surface is: u u/c uc 2u A point source of radiation emits power P uniformly in all directions. The amplitude of the electric field at a distance r from the source is proportional to: 1/r 1/r 2 1/r r If the electric field amplitude of an EM wave is E 0 , what is the energy density associated with the electric field? 1 4 0 E 0 2 1 2 0 E 0 2 0 E 0 2 2 0 E 0 2 The ratio of the speed of an electromagnetic wave in vacuum to its speed in a medium of relative permittivity r and relative permeability r is: r r 1 r r r r r r The speed of light in vacuum ( c ) is related to the permeability ( 0 ) and permittivity ( 0 ) as c = 1/ 0 0 . This relationship was first derived from: Maxwell's equations Faraday's laws Gauss's law Ampere's law An electromagnetic wave with frequency and wavelength is traveling in vacuum. If the maximum value of the electric field is E 0 , the average power per unit area transported by the wave is: 1 2 c 0 E 0 2 c 0 E 0 2 1 2 E 0 2 0 c E 0 2 2 0 Which of the following is the correct expression for the displacement current density J d ? 0 E t 1 0 B t 0 E t 0 0 E t In an electromagnetic wave, the amplitude of the magnetic field is B 0 and the amplitude of the electric field is E 0 . The total average energy density is: 1 2 0 E 0 2 0 E 0 2 B 0 2 0 1 2 B 0 2 0 A plane electromagnetic wave of frequency 28 MHz travels in free space along the x -direction. At a particular point and time, E = 6.3 j V/m . What is B at this point? 2.1 10 -8 k T 2.1 10 -8 j T 18.9 10 -8 k T 6.3 k T If the electric field in a plane electromagnetic wave is given by E = 150 (1.2 10 7 z - 3.6 10 15 t) i , what is the refractive index of the medium? 1.2 1.5 1.0 2.0 The radiation pressure of an electromagnetic wave of intensity I incident normally on a perfectly reflecting surface is: 2I/c I/c I/2c Ic In a transverse electromagnetic wave, the directions of the electric field E , magnetic field B , and wave propagation k are related as: E B = 0, E k = 0, B k = 0 E B = 0 E B 0 E B A radio wave of frequency 10 6 Hz propagates in a medium with relative permittivity 4.0 . Its wavelength in the medium is: 150 m 300 m 75 m 600 m The magnetic field in a plane electromagnetic wave is given by B = B 0 (kx - t) . The average energy density of the magnetic field is: B 0 2 4 0 B 0 2 2 0 B 0 2 0 0 B 0 2 2 The speed of an electromagnetic wave in a non-magnetic medium is 1.5 10 8 m/s . If the relative permeability of the medium is 1.0 , the relative permittivity of the medium is: 4.0 2.0 1.5 2.25 If the electric field of a wave is E = E 0 ( t + kz) and the wave propagates along the negative z -axis, what is the direction of the magnetic field? Perpendicular to both z-axis and electric field direction Parallel to the electric field direction Along the positive z-direction Parallel to the propagation direction An electromagnetic wave with an intensity of I = 15 W/m 2 is incident normally on a small surface that is perfectly absorbing. If the area of the surface is A = 2 cm 2 , the force exerted by the wave on the surface is: 10 -11 N 10 -10 N 3 10 -11 N 2 10 -9 N An electromagnetic wave is incident normally on a perfectly reflecting mirror. If the momentum delivered to the mirror is p in a time t , and the energy incident is U , then: p = 2U/c p = U/c p = U/2c p = U/c 2 The amplitude of the oscillating magnetic field in a plane electromagnetic wave is B 0 = 510 nT . The RMS value of the electric field is approximately: 108 V/m 153 V/m 510 V/m 76 V/m The ratio of the magnitude of the magnetic force ( F m ) to the magnitude of the electric force ( F e ) exerted on a particle of charge q moving with velocity v in an electromagnetic wave is (assuming v is perpendicular to B ): v/c c/v 1 v 2/c 2 The electric field of an electromagnetic wave is given by E = 100 (2 10 8 t - kx) . The peak energy density of the wave is: 8.85 10 -8 J/m 3 4.42 10 -8 J/m 3 1.77 10 -7 J/m 3 2.21 10 -8 J/m 3 In an electromagnetic wave in free space, the root mean square value of the electric field is E rms = 6 V/m . The peak value of the magnetic field is: 2.83 10 -8 T 0.70 10 -8 T 4.23 10 -8 T 1.41 10 -8 T Which of the following Maxwell's equations essentially states that magnetic monopoles do not exist? B d A = 0 E d A = Q encl 0 E d l = - d B dt B d l = 0 (I c + I d) In a plane electromagnetic wave, the ratio of the average energy density associated with the magnetic field to the total average energy density is: 1/2 1 1/4 2 The displacement current between the plates of a parallel plate capacitor is 1.5 A when it is being charged. The rate of change of electric flux through the space between the plates is: 1.69 10 11 V m/s 1.32 10 11 V m/s 1.5 10 12 V m/s 1.77 10 10 V m/s A plane EM wave of frequency 30 MHz travels in vacuum along the x -direction. The magnetic field at a point is B = 2 10 -8 k T . The electric field at that point is: 6 j V/m 6 k V/m -6 j V/m 6 i V/m According to Maxwell's modification of Ampere's law, a magnetic field can be produced by a conduction current and by a: Time-varying electric field Static electric field Static magnetic field Time-varying gravitational field The average value of the Poynting vector for a plane electromagnetic wave is given by: E 0 B 0 2 0 E 0 B 0 0 E 0 2 0 c B 0 2 2 0 A parallel plate capacitor is being charged. The area of each plate is A and the separation is d . If the rate of change of electric field is dE/dt , then the displacement current is: 0 A dE dt 0 A d dE dt 0 A dE dt 0 d dE dt Which component of the electromagnetic wave is responsible for the pressure exerted by it on a surface? Both electric and magnetic fields Only the electric field Only the magnetic field Neither electric nor magnetic field A plane electromagnetic wave is incident normally on a surface of area A . If the average intensity is I , the total force exerted by the wave on a perfectly reflecting surface is: 2IA c IA c IA 2c 2I c The electric field part of an EM wave in vacuum is E = E 0 (kz - t) . The associated magnetic field B is along which direction if E is along i ? j - j k i For a plane electromagnetic wave propagating in the z -direction, the fields can be represented as: E x = E 0 (kz- t), B y = B 0 (kz- t) E x = E 0 (kz- t), B x = B 0 (kz- t) E z = E 0 (kz- t), B z = B 0 (kz- t) E y = E 0 (kz- t), B y = B 0 (kz- t) The dimensional formula for the product of permittivity of free space ( 0) and the square of the electric field (E 2) represents which physical quantity? Energy density Power Pressure Force Which of the following Maxwell's equations is derived from Faraday's law of induction? E d l = - d B dt B d A = 0 E d A = q 0 B d l = 0 I c + 0 0 d E dt A plane electromagnetic wave is propagating along the z -direction. If the electric field is E = E 0 (kz - t) i , then the magnetic field B is: B = E 0 c (kz - t) j B = E 0 c (kz - t) j B = E 0 c (kz - t) k B = - E 0 c (kz - t) j An electromagnetic wave of intensity 1.5 kW/m 2 is incident normally on a perfectly absorbing surface of area 2 m 2 . The force exerted on the surface is: 10 10 -6 N 5 10 -6 N 15 10 -6 N 20 10 -6 N Identify the incorrect statement regarding electromagnetic waves. In vacuum, waves of different frequencies travel at different speeds They are transverse in nature They exert pressure on the surface they strike They do not require a material medium for propagation The electric field part of an EM wave is given by E x = 0, E y = 50 (10 15 t - 10 15 c z), E z = 0 . The average intensity of this wave is: 3.32 W/m 2 6.64 W/m 2 1.66 W/m 2 5.00 W/m 2 Radio waves of frequency 3 10 7 Hz propagate in a non-magnetic medium of relative permittivity 9 . The speed and wavelength in the medium are: 10 8 m/s , 3.33 m 3 10 8 m/s , 10 m 10 8 m/s , 10 m 3 10 7 m/s , 1 m If the amplitude of the electric field in an EM wave is E 0 = 120 N/C , what is the intensity of the wave? 19.1 W/m 2 38.2 W/m 2 9.5 W/m 2 4.8 W/m 2 The energy of an electromagnetic wave is U . If the wave is reflected normally by a mirror, the change in momentum of the mirror is: 2U/c U/c Uc 2Uc The electric field part of an electromagnetic wave in a medium is represented by : E x=0 E y=2.5 N C [ (2 10 6 rad m )t- ( 10 -2 rad s )x ] E z=0 . The wave is : Moving along -x direction with frequency 10 6 Hz and wavelength 200m Moving along y direction with frequency 2 10 6 Hz and wavelength 200m Moving along x direction with frequency 10 6 Hz and wavelength 100m Moving along x direction with frequency 10 6 Hz and wavelength 200m For a plane electromagnetic wave propagating in x -direction, which one of the following combination gives the correct possible directions for electric field (E) and magnetic field (B) respectively? - j + k , - j - k j + k , - j - k - j + k , - j + k j + k , j + k Match List-I with List-II array llll ; & List-I (Electromagnetic waves) & ; & List-II (Wavelength) (a) & AM radio waves & (i) & 10 -10 m (b) & Microwaves & (ii) & 10 2 m (c) & Infrared radiations & (iii) & 10 -2 m (d) & X-rays & (iv) & 10 -4 m array Choose the correct answer from the options given below (a) - (iii), (b) - (ii), (c) - (i), (d) - (iv) (a) - (iii), (b) - (iv), (c) - (ii), (d) - (i) (a) - (ii), (b) - (iii), (c) - (iv), (d) - (i) (a) - (iv), (b) - (iii), (c) - (ii), (d) - (i) The amplitude of the magnetic field in an EM wave is B 0 = 1.6 10 -7 T . If the frequency is 30 MHz , the expression for the electric field is: E z = 48 (0.63x - 1.88 10 8 t) V m E z = 4.8 (0.63x - 1.88 10 8 t) V m E z = 48 (0.31x - 1.88 10 8 t) V m E z = 0.48 (0.63x - 1.88 10 8 t) V m Total energy density u of an electromagnetic wave is given by: ε 0 E 2 1 2 ε 0 E 2 B 2 2μ 0 1 4 ε 0 E 2 The speed of an electromagnetic wave in a medium of dielectric constant 2.25 and relative permeability 4 is: 10 8 m/s 3 × 10 8 m/s 2 × 10 8 m/s 0.5 × 10 8 m/s A plane electromagnetic wave is travelling in the positive x -direction in vacuum. Which of the following sets of electric field ( E ) and magnetic field ( B ) directions are possible? E along +y, B along +z E along +z, B along +y E along +y, B along -z E along -z, B along -y An electromagnetic wave is moving along the negative x -direction. At a certain point, the electric field is along the positive y -axis. The direction of the magnetic field at that point is: Positive z -direction Negative z -direction Positive x -direction Negative y -direction If the electric field of a plane electromagnetic wave is given by E = E 0 j (kz - t) , then the associated magnetic field B is: B = E 0 c i (kz - t) B = E 0 c i (kz - t) B = E 0 c k (kz - t) B = - E 0 c i (kz - t) An electromagnetic wave is incident on a surface with an average intensity of 0.6 W/m 2 . If the surface is perfectly absorbing and has an area of 20 cm 2 , the average force exerted on the surface is: 4 10 -12 N 2 10 -12 N 1.2 10 -11 N 6 10 -12 N In an EM wave, the amplitude of the electric field is 10 V/m . The magnitude of the maximum Poynting vector is: 0.265 W/m 2 0.132 W/m 2 0.530 W/m 2 1.060 W/m 2 If E 0 = 60 V/m for an EM wave, what is the average energy density of the wave? 1.59 10 -8 J/m 3 3.18 10 -8 J/m 3 7.95 10 -9 J/m 3 6.36 10 -8 J/m 3 A point source of electromagnetic radiation has an average power output of 800 W . The maximum value of the electric field at a distance of 3.5 m from the source is: 62.6 V/m 44.3 V/m 125.2 V/m 31.3 V/m The wave impedance of free space is defined as the ratio of E 0 to H 0 . Its value is approximately: 377 120 50 3 10 8 If the average intensity of sunlight reaching the Earth's surface is 1360 W/m 2 , what is the root mean square (rms) value of the electric field strength? 716 V/m 1012 V/m 540 V/m 377 V/m The pressure exerted by an electromagnetic wave of intensity I on a surface which absorbs 50 % of the incident radiation and reflects the other 50 % normally is: 1.5 I c I c 2I c 0.5 I c In an electromagnetic wave, the amplitude of the magnetic field is H 0 . The amplitude of the electric field E 0 is given by: H 0 0 0 H 0 0 0 H 0 ( 0 0) H 0 0 0 The speed of electromagnetic waves in a medium of relative permittivity r = 9 and relative permeability r = 1 is: 10 8 m/s 3 10 8 m/s 0.33 10 8 m/s 9 10 8 m/s If the electric field vector is E = E 0 (kz - t) j , what is the corresponding magnetic field vector B ? - E 0 c (kz - t) i E 0 c (kz - t) i E 0 c (kz - t) k - E 0 c (kz - t) j The dimension of the quantity 0 0 is the same as that of: Resistance Inductance Capacitance Velocity The magnetic field in a plane electromagnetic wave is given by B x = B y = 0 , B z = (2 10 -7 T ) (0.5 10 3 x + 1.5 10 11 t) . The expression for the electric field will be: E y = (60 V/m ) (0.5 10 3 x + 1.5 10 11 t) E z = (60 V/m ) (0.5 10 3 x + 1.5 10 11 t) E y = (2 10 -7 V/m ) (0.5 10 3 x + 1.5 10 11 t) E x = (60 V/m ) (0.5 10 3 x + 1.5 10 11 t) In an EM wave, the amplitude of the magnetic field is 1.2 10 -7 T . What is the average intensity of the wave? 1.72 W/m 2 3.44 W/m 2 0.86 W/m 2 5.16 W/m 2 The magnetic field in a plane electromagnetic wave is given by B = B 0 (kx + t) j . The expression for the corresponding electric field E is: E = c B 0 (kx + t) k E = -c B 0 (kx + t) k E = c B 0 (kx + t) i E = -c B 0 (kx + t) j A parallel plate capacitor has plate area A and separation d . It is being charged by a current I . The magnitude of magnetic field at a point distance r ( r < R , where R is the radius of the plates) from the axis of the plates is: 0 I r 2 R 2 0 I 2 r 0 I r 2 2 R 2 Zero The magnetic field amplitude of an electromagnetic wave in vacuum is B 0 = 510 nT . If the wave is incident on a surface and is completely absorbed, the radiation pressure is: 1.03 10 -7 N/m 2 2.06 10 -7 N/m 2 5.10 10 -7 N/m 2 0.51 10 -7 N/m 2 An electromagnetic wave is propagating through a medium with refractive index n=2 . If the electric field amplitude is E 0 = 100 V/m , the magnetic field amplitude B 0 in the medium is: 6.67 10 -7 T 3.33 10 -7 T 1.50 10 -7 T 2.00 10 -7 T Which of the following is the dimensional formula for the quantity 0 c , where 0 is the permeability of free space and c is the speed of light? [M L 2 T -3 A -2 ] [M L T -3 A -1 ] [M L 2 T -2 A -2 ] [M L 0 T -2 A -1 ] The radiation pressure exerted by an electromagnetic wave of intensity I on a surface that is 25 % reflecting and 75 % absorbing at normal incidence is: 1.25 I/c 1.75 I/c 2.0 I/c 0.75 I/c The phase difference between the electric and magnetic field vectors in an electromagnetic wave is: 0 π/2 π π/4 The magnetic field in a plane electromagnetic wave is given by B y = 2 10 -7 (0.5 10 3 x + 1.5 10 11 t) T . The expression for the electric field is: E z = 60 (0.5 10 3 x + 1.5 10 11 t) V/m E z = 30 (0.5 10 3 x + 1.5 10 11 t) V/m E y = 60 (0.5 10 3 x + 1.5 10 11 t) V/m E x = 60 (0.5 10 3 x + 1.5 10 11 t) V/m The energy density of an EM wave in vacuum is 10 -6 J/m 3 . What is the peak value of the electric field? 475 V/m 150 V/m 335 V/m 225 V/m If the peak value of the electric field in an EM wave is E 0 , then the peak energy density is: 0 E 0 2 1 2 0 E 0 2 2 0 E 0 2 1 4 0 E 0 2 A parallel plate capacitor is charged by an external source. The magnetic field at a point midway between the plates and at a distance r from the central axis (where r is less than the plate radius R ) is proportional to: r 1/r r 2 1/r 2 Which scientist predicted that the 'ether' (a supposed medium for light) does not exist, paving the way for the understanding of EM waves in vacuum? Einstein Maxwell Hertz Marconi The dimension of the ratio E B in an electromagnetic wave is the same as that of: Velocity Acceleration Force Electric current If an electromagnetic wave of energy U is incident normally on a perfectly absorbing surface, the momentum delivered to the surface is: U/c 2U/c Uc 0 The amplitude of the magnetic field of an electromagnetic wave is B 0 . The amplitude of the electric field E 0 is given by E 0 = c B 0 . What are the units of E 0/B 0 ? m/s s/m N/C Tesla Maxwell's modification of Ampere's law, B d l = 0 (I c + 0 d E dt ) , is known as: Ampere-Maxwell Law Faraday's Law Lenz's Law Gauss's Law An electromagnetic wave has a frequency of 100 MHz and propagates in a non-magnetic medium with relative permittivity r = 4.0 . Its speed in the medium is: 1.5 10 8 m/s 3 10 8 m/s 0.75 10 8 m/s 6 10 8 m/s The oscillating electric and magnetic field vectors in an electromagnetic wave are oriented: Perpendicular to each other and to the direction of propagation Parallel to each other and to the direction of propagation Perpendicular to each other and parallel to the direction of propagation Parallel to each other and perpendicular to the direction of propagation Calculate the displacement current when the charge on the plates of a 2 F capacitor is changing at a rate of 5 C/s . 5 A 10 A 2.5 A 0.4 A Which of the following does not change when an electromagnetic wave travels from vacuum into a glass slab? Frequency Wavelength Velocity Amplitude An electromagnetic wave is propagating in a medium where the relative permittivity is r = 4 and the relative permeability is r = 1 . The speed of the wave in this medium is: 1.5 10 8 m/s 3.0 10 8 m/s 0.75 10 8 m/s 6.0 10 8 m/s The ratio of the average energy density of the magnetic field to the total average energy density of an electromagnetic wave in vacuum is: 1/2 1/4 1 2 In an electromagnetic wave, if the RMS value of the electric field is E rms = 30 V/m , the RMS value of the magnetic field B rms is: 10 -7 T 10 -8 T 3 10 -7 T 9 10 -9 T For an electromagnetic wave, the phase of the electric field and the magnetic field are: In phase Out of phase by /2 Out of phase by Out of phase by 2 The phenomenon of 'polarization' in electromagnetic waves proves that these waves are: Transverse Longitudinal Mechanical Stationary The displacement current between the plates of a parallel plate capacitor is 2 A . If the area of the plates is 10 cm 2 , the displacement current density is: 2000 A/m 2 0.2 A/m 2 20 A/m 2 2 A/m 2 The speed of electromagnetic waves in a medium is v . If the relative permittivity r of the medium is 2.25 and the relative permeability r is 1.0 , the refractive index of the medium is: 1.5 2.25 1.25 1.0 In an electromagnetic wave, the electric and magnetic fields are: In phase and perpendicular to each other In phase and parallel to each other 90 out of phase and perpendicular to each other 180 out of phase and perpendicular to each other Which of the following physical quantities has the same dimensions as the speed of light c ? 1 0 0 0 0 0 0 0 0 The ratio of amplitude of magnetic field to the amplitude of electric field for an electromagnetic wave propagating in vacuum is: Reciprocal of speed of light Speed of light Ratio of μ 0 to ε 0 Unity The oscillating magnetic field of a plane electromagnetic wave is given by B y = 8 10 -6 [2 10 11 t + 300x] T . The direction of propagation is along: Negative x -direction Positive x -direction Positive y -direction Negative y -direction In an electromagnetic wave, the energy is carried by: Both electric and magnetic fields Electric field only Magnetic field only The medium only The dimension of 1 0 ε 0 is: [L 2 T -2 ] [L T -1 ] [L -2 T 2] [L -1 T] During the charging of a capacitor, the displacement current exists: Only in the region between the plates Only in the wires Both in wires and between plates Neither in wires nor between plates What is the ratio of energy density of the electric field to the total energy density of an electromagnetic wave in vacuum? 1/2 1/4 1 2 Which physical property of an electromagnetic wave confirms its transverse nature? Polarization Interference Diffraction Refraction If the momentum of an electromagnetic wave is p , and its energy is U , then the relationship is: p = U c p = Uc p = U c 2 p = √ Uc Who first predicted the existence of electromagnetic waves theoretically? Maxwell Hertz Marconi Newton In a plane electromagnetic wave, the ratio of the energy carried by the electric field to the energy carried by the magnetic field is: 1:1 1:2 2:1 √ 2 :1 The value of the displacement current between the plates of a capacitor is equal to: 0 d E dt 1 0 d E dt μ 0 d B dt 1 μ 0 d B dt Which of the following describes the relationship between the electric field E and magnetic field B at any point in an electromagnetic wave? E = cB B = cE E = c 2 B B = c 2 E The source of electromagnetic waves is: An accelerating charge A charge moving with constant velocity A stationary charge A neutral atom For a plane electromagnetic wave, the electric field is → E = E 0 i sin (ωt + kx) . The wave is propagating along: Negative x -axis Positive x -axis Positive y -axis Negative z -axis What is the displacement current in a wire where the conduction current is constant at 5 A ? 0 5 A 2.5 A Infinite Electromagnetic waves are produced by: An accelerating charge A charge at rest A charge moving with constant velocity A neutral particle An electromagnetic wave is represented by E = E 0 [10 7 x + 3 10 15 t] . What is the speed of this wave? 3 10 8 m/s 10 8 m/s 3 10 7 m/s 10 7 m/s A radiation of energy E falls normally on a perfectly reflecting surface. The momentum transferred to the surface is: 2E/c E/c Ec E/c 2 Dimensions of 0 d E dt are same as that of: Electric current Electric charge Magnetic field Electric potential The velocity of electromagnetic radiation in a medium of permittivity 0 and permeability 0 is given by: 1 / 0 0 0 / 0 0 / 0 0 0 The condition for a wave to be a plane electromagnetic wave is that the electric field E and magnetic field B must be: Perpendicular to each other and perpendicular to the direction of propagation Parallel to each other and perpendicular to the direction of propagation Perpendicular to each other and parallel to the direction of propagation Parallel to each other and parallel to the direction of propagation According to Maxwell, a changing electric field produces: A magnetic field An electric current A constant electric field No field Which scientist experimentally confirmed the existence of electromagnetic waves? Heinrich Hertz James Clerk Maxwell Michael Faraday Guglielmo Marconi Electromagnetic waves do not transport: Charge Energy Momentum Information The source of all electromagnetic waves is: An accelerating charge A charge moving with constant velocity A stationary charge A magnetic monopole Which of the following Maxwell's equations implies that magnetic monopoles do not exist? B d A = 0 E d l = - d B dt E d A = q 0 B d l = 0 (I c + I d) A plane electromagnetic wave travels in vacuum along the z -direction. What can you say about its electric and magnetic field vectors? E and B are in the xy -plane and are mutually perpendicular E is along z , B is along x E and B are both along the z -direction E is along y , B is along z The speed of electromagnetic waves in a vacuum is given by: 1 0 ε 0 0 ε 0 μ 0 ε 0 ε 0 μ 0 The displacement current flows in the dielectric of a capacitor only when the potential difference across the plates is: Changing with time Constant and very high Zero Constant and very low The wavefront of a plane electromagnetic wave is: A plane perpendicular to the direction of propagation A sphere with the source at the center A plane parallel to the direction of propagation A cylinder with the source at the axis If E and B represent the electric and magnetic field vectors of an electromagnetic wave, then the direction of propagation of the wave is that of: E × B B × E E B If the electric field component of an EM wave is given by E = E 0 (kz - t) , then the direction of the Poynting vector is along the: +z direction -z direction +x direction +y direction For a medium with permittivity and permeability , the velocity of electromagnetic waves is given by: 1 1 A parallel plate capacitor is being charged. At a certain instant, the displacement current is 2 A . What is the conduction current in the connecting wires? 2 A 1 A 4 A Zero In an EM wave, the amplitude of the electric field is 600 V/m . What is the amplitude of the magnetic field? 2 10 -6 T 2 10 -7 T 1.8 10 10 T 6 10 -7 T The unit of the Poynting vector is: W/m 2 J/m 2 V/m Tesla A plane electromagnetic wave is propagating in vacuum along the x -direction. The magnetic field component is given by B y = 2 10 -7 (0.5 10 3 x - 1.5 10 11 t) T . What is the peak value of the electric field? 60 V/m 30 V/m 2 10 -7 V/m 0.5 10 3 V/m The oscillation of an electric charge produces an electromagnetic wave. If the charge oscillates with a frequency of 100 MHz , the frequency of the produced electromagnetic wave is: 100 MHz 200 MHz 50 MHz 10 GHz A plane electromagnetic wave is travelling in the +y direction. At a certain point P , the electric field E is along the +x axis. The direction of the magnetic field B at this point is: Along +z axis Along -z axis Along +x axis Along -x axis Which scientist used a spark gap generator and a receiver loop to experimentally prove the existence of EM waves? Heinrich Hertz James Clerk Maxwell Guglielmo Marconi Jagadish Chandra Bose If v , x and m represent the wavelengths of visible light, x-rays and microwaves respectively, then- m> x> v v> m> x v> x> m m> v> x The electric and magnetic field of an electromagnetic wave are in opposite phase and perpendicular to each other in opposite phase and parallel to each other in phase and perpendicular to each other in phase and parallel to each other. The condition under which a microwave oven heats up a food item containing water molecules most efficiently is The frequency of the microwaves must match the resonant frequency of the water molecules The frequency of the microwaves has no relation with natural frequency of water molecules Microwaves are heat waves, so always produce heating Infra-red waves produce heating in a microwave oven The value of Planck's constant is 6.63 10 -34 Js . The speed of light is 3 10 17 nm s -1 . Which value is the closest to the wavelength in nanometer of a quantum of light with frequency of 6 10 15 s -1 ? 10 25 50 75 Light with an energy flux of 25 10 4 Wm -2 falls on a perfectly reflecting surface at normal incidence. If the surface area is 15 cm 2 , the average force exerted on the surface is :- 1.25 10 -6 N 2.50 10 -6 N 1.20 10 -6 N 3.0 10 -6 N Out of the following options which one can be used to produce a propagating electromagnetic wave ? A charge moving at constant velocity A stationary charge A chargeless particle An accelerating charge Inside a parallel plate capacitor the electric field E varies with time as t 2 . The variation of induced magnetic field with time is given by : t 2 no variation t 3 t An em wave is propagating in a medium with a velocity V =V i . The instantaneous oscillating electric field of this em wave is along +y axis. Then the direction of oscillating magnetic field of the em wave will be along -y direction +z direction -z direction -x direction Which colour of the light has the longest wavelength? Violet Red Blue Green The maximum value of the electric field in an electromagnetic wave is E 0 = 600 V/m . What is the maximum value of the magnetic field B 0 ? 2 10 -6 T 1.8 10 5 T 2 10 -5 T 3 10 -7 T The ratio of contributions made by the electric field and magnetic field components to the intensity of an electromagnetic wave is : (c = speed of electromagnetic waves ) 1 : 1 1 : c 1 : c 2 c : 1 Light with an average flux of 20 W/cm 2 falls on a non-reflecting surface at normal incidence having surface area 20 cm 2 . The energy received by the surface during time span of 1 minute is : 12 10 3 J 24 10 3 J 48 10 3 J 10 10 3 J A particular station of All India Radio, New Delhi broadcasts on a frequency of 1,368 kHz (kilohertz). The wavelength of the electromagnetic radiation emitted by the transmitter is : [speed of light c = 3.0 10 8 ms -1 ] 219.2 m 2192 m 21.92 cm 219.3 m When light propagates through a material medium of relative permittivity r and relative permeability r , the velocity of light, v is given by ( c -velocity of light in vacuum) v = r r v = r r v = c r r v = c The minimum wavelength of X-rays produced by an electron accelerated through a potential difference of V volts is proportional to V 1 V 1 V V 2 In a plane electromagnetic wave travelling in free space, the electric field component oscillates sinusoidally at a frequency of 2.0 10 10 Hz and amplitude 48 V m -1 . Then the amplitude of oscillating magnetic field is (Speed of light in free space = 3 10 8 m s -1 ) 1.6 10 -9 T 1.6 10 -8 T 1.6 10 -7 T 1.6 10 -6 T The property which is not of an electromagnetic wave travelling in free space is that: They are transverse in nature The energy density in electric field is equal to energy density in magnetic field They travel with a speed equal to 1 0 0 They originate from charges moving with uniform speed The electric field in a plane electromagnetic wave is given by E z = 60 (5x + 1.5 10 9 t) V/m . Then expression for the corresponding magnetic field is (here subscripts denote the direction of the field) : B y = 60 (5x + 1.5 10 9 t) T B y = 2 10 -7 (5x + 1.5 10 9 t) T B x = 2 10 -7 (5x + 1.5 10 9 t) T B z = 60 (5x + 1.5 10 9 t) T Match List I with List II: array llll ; & List-I (Electromagnetic wave) & ; & List-II (Production) A. & Microwave & I. & Electrons in atoms emit light when they move from a higher energy level to a lower energy level. B. & Visible light & II. & Radioactive decay of nucleus C. & Gamma rays & III. & Vibration of atoms and molecules D. & Infra-red rays & IV. & Klystron valve or magnetron valve array A–IV, B–III, C–II, D–I A–III, B–IV, C–I, D–II A–III, B–I, C–II, D–IV A–IV, B–I, C–II, D–III Which of the following Maxwell's equations is modified to include the concept of displacement current? Ē dĦ = μ 0(I c + ε 0 dΦ E dt ) Ē dA = Q ε 0 Ē dı = - dΦ B dt Ē dA = 0 The dimension of the intrinsic impedance of free space, denoted by 0 = 0 0 , is equivalent to the dimension of: Resistance Inductance Capacitance Current In an electromagnetic wave, the ratio of the average energy density of the electric field to the average energy density of the magnetic field is: 1:1 μ 0 ε 0 : 1 ε 0 : μ 0 ᵅ : 1 A plane electromagnetic wave is propagating along the x -direction. If the electric field vector E is along the y -axis, the magnetic field vector B must be along the: z -axis -z -axis x -axis -y -axis The electric field part of an electromagnetic wave in a medium is represented by E x = 0 , E y = 2.5 N C [(2π 10 6 rad s ) t - (π 10 -2 rad m ) x] , and E z = 0 . The wave is moving along: positive x -direction with frequency 10 6 Hz negative x -direction with frequency 10 6 Hz positive z -direction with frequency 2π 10 6 Hz negative x -direction with frequency 10 6 Hz Find the magnetic field amplitude B 0 if the electric field amplitude is E 0 = 120 N/C and the wave is in vacuum. 400 nT 40 nT 1.2 αT 36 αT An electromagnetic wave of intensity I falls on a non-reflecting surface. The radiation pressure exerted by it is: I/c 2I/c Ic I/c 2 A capacitor of capacitance C is being charged by a DC source V . The displacement current between the plates when the capacitor is fully charged is: Zero V/R CV Infinite A parallel plate capacitor with plate area A and separation d is being charged by a time-varying voltage V(t) . The displacement current I d between the plates is given by: 0 A dV dt 1 d 0 A d V A d dV dt 0 A d dV dt If an electromagnetic wave of energy U is incident on a perfectly reflecting surface at normal incidence, the momentum delivered to the surface is: 2U c U c U c 2 2U c 2 The refractive index of a medium is 1.5 and its relative permeability is 1.0 . The relative permittivity of the medium is: 2.25 1.5 0.67 3.0 An electromagnetic wave is propagating along the z -direction. If the electric field vector is → E = E 0 i cos (kz - ωt) , then the magnetic field vector → B is: → B = E 0 c J cos (kz - ωt) → B = E 0 c J cos (kz - ωt) → B = E 0 c i cos (kz - ωt) → B = - E 0 c J cos (kz - ωt)