INSTITUTE OF AERONAUTICAL ENGINEERING Dundigal, Hyderabad Electronics and Communicaton Engineering

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1 INSTITUTE OF AERONAUTICAL ENGINEERING Dundigal, Hyderabad Electronics and Communicaton Engineering Question Bank Course Name : Electromagnetic Theory and Transmission Lines (EMTL) Course Code : A404 Class : II - B. Tech Branch : ECE Year : Course Coordinator : Mrs Usha rani Course Faculty : G.anil reddy,seethaiah OBJECTIVES To introduce the student to the fundamental theory and concept of electromagnetic waves and transmission lines, and their practical applications. To study the propagation, reflection, and transmission of plane waves in bounded and unbounded media.. Group - A (Short Answer Questions) UNIT-I ELECTROSTATICS Define coulombs law? 2 find the electric field E, if the force on a stationary charge Q is F? Define unit vector? 4 Specify the importance of divergence and stokes theorems? Course Define gauss law? Give the expression for the potential difference of two concentric conducting sphere of radius a and b? List the applications of gauss law? Define electric flux and give the expression? Give the relation between electric flux and flux density? 0 State the divergence theorem and give the expression? P a g e

2 Course State the stokes theorem and give the expression? 2 Define electric potential? What e is the first Maxwell s equation? Analysis 4 Give the relation between V and E? 0 What is the value of curl of E for a static field? Give the expression for energy due to point Q in electricfield? What is the condition that the electrostatic field is conservative? Application What is mean by dipole moment? Give the expression for the energy density for electrostatic fields? 20 Find the value of aθ.aφ? Define convention current density? 22 Define conduction current density? 2 List the names of few conductors along with its conductivity? 24 Define polarization? 2 Give the expression continuity equation? 2 Give the expression for relaxation time? 2 Writ e boundary conditions for conducting media? Analysis 2 Writ e boundary conditions for dielectric media? 2 Define poission and laplace equations? 0 Define capacitance between two parallel plates? Analysis What are the different types capacitors give the C value for all? UNIT-II MAGNETOSTATICS Define Biot severt law and give the expression? 2 Define amperes circuit law and give the expression? Analysis List the applications of amperes circuit law? 4 What is 2 nd Maxwell s equation? What is nd Maxwell s equation? Define magnetic flux density? Specify the units? Define magnetic scalar potential and give the expression? 2 P a g e

3 Course Define magnetic vector potential and give the expression? What is the value of permeability for free space and specify the units? 0 Lis t the types of forces exerted by the magnetic field? What is lenz law? 2 What is the Lorentz force equation for a static charge? What is the Lorentz force equation for a DC charge? 4 What is mean by magnetic dipole moment? List the boundary conditions for Magnetic fields? Define inductance? Define mutual inductance? What Neumann s formula for mutual inductance? List any two differences between self and mutual inductance? 20 Define magnetic energy? Define magnetic energy due to mutual inductance? 22 What are the different types of magnetic materials? 2 List any two differences between magnetic materials? 24 List any two differences between electrostatic fields and magneto static fields? 2 Define faraday law? 2 What is mean by transformer emf? 2 What is mean by generator emf? 2 Give the reason why amperes law is inconsistent? 2 Define displacement current density? 0 Specify the conditions for free space? P a g e

4 Course Specify the conditions conductor and dielectrics? 2 What is mean by sinusoidal harmonic variations? UNIT-III EM WAVE CHARACTERISTICS What is mean by homogeneous medium? 2 What is mean by isotropic medium? What is mean by linear medium? 4 Define uniform plane wave? Define characteristics impedance? Give the expression for attenuation constant? Give the expression for phase constant? Define skin depth? Define Snell s law? 0 Define reflection coefficient? Define transmission coefficient? 2 Define Brewster angle? Define critical angle? 4 What is mean by total internal reflection? Define surface impedance? Define poynting theorem? 2 Give the expression for reflection coefficient for vertical polarization with oblique incidence? Give the expression for transmission coefficient for horizontal polarization with oblique incidence? Give the expression for reflection coefficient for normal incidence? 4 P a g e

5 Course 20 Give the expression for transmission coefficient for normal incidence? 2 UNIT-IV TRANSMISSION LINES- I Define transmission line? 2 What are the types of transmission lines? What are the primary parameters of transmission lines? 4 What are the secondary parameters of transmission lines? What are the generalized equation of transmission lines? Define characteristic impedance of a transmission lines? Define group velocity of transmission lines? Specify the relation between group velocity and phase velocity of transmission lines? Give the condition for lossless transmission in transmission lines? 0 Give the condition for distortion less transmission in transmission lines? Give the condition for maximum attenuation in transmission lines? 2 What is mean by line distortion in transmission lines? What are various loads in transmission lines? 4 What is use of generalize transmission line equations? What is maximum range of frequency transmission lines? UNIT-V TRANSMISSION LINES- II What is mean by standing wave? 2 Define reflection in transmission line? Define refraction in transmission line? 4 Give the expression for reflection coefficient in transmission line? What are types of standing wave ratios in transmission line? Specify the relation between VSWR and reflection coefficient in transmission P a g e

6 line? Give the expression for input impedance inters of reflection coefficient? Course What is the use of impedance transformation? What is mean by stub matching? 0 What are the advantages of stub matching? What is the use of smith chart? 2 What are the properties of stub matching? List the application of smith chart? 2. Group - II (Long Answer Questions) S. No Question UNIT-I ELETROSTATICS Define divergence and divergence theorem of a vector A and write the equations? Program 2 Determine the divergence of T = r 2 cos θ a r + r sin θ cos a θ + cos θ a? Define dielectric constant, dielectric strength and relaxation time in electrostatics? 4 Derive equation of continuity? Define curl of a vector and state Stoke s theorem? Determine the curl of Q = ρ sin a ρ + ρ 2 za + z cos a z? Write a Laplacian equation on Cartesian, cylindrical and spherical coordinates? Explain conduction current and derive the expression for conduction current density? State coulomb s law and write the equation for F that exist between two unlike charges? 0 Derive the expression for electric field on point charge Q due to the point charge Q? P a g e

7 Program S. No Question Explain convection current density and derive expression for it? 2 State Gauss s law and obtain the firstmaxwell s equation for electrostatic fields? What is the boundary value problem? Write steps to calculate resistance of a conductor? 4 Obtain the expression for the capacitance of a coaxial capacitor? UNIT-II MAGNETOSATICS State Biot-Savart s law and obtain the expression for magnetic field intensity at a point P due to line current element? 2 State and explain Faraday s law for time varying field? Show that E m = (u B) for time varying fields? 4 Define magnetic flux density? Why magnetic flux density is zero in a closed surface? Show that H = J + D t? State and explain ampere s circuit law? Obtain the expression for magnetic field intensity due to infinite line current element? What is transformer emf? Show that E = B t Write integral form of all MAXWELL S equations? 0 Obtain Lorentz s force equation? Obtain the expression for force F on current element due to the magnetic field B? 2 Write MAXWELL S equations in differential form? Show that the displacement current density J d = D t? UNIT-III EM WAVE CHARACTERISTICS Derive Helmholtz equations? 2 State poynting theorem. What does the poynting vector represent? Derive the relation between E and H in free space? 4 What is polarization? What are the different types of polarization? P a g e

8 S. No Question Program Define conducting medium and obtain the expression for intrinsic impedance? 4 What is normal incidence and discuss? Determine the reflected wave Hr, Er and the transmitted wave Et. Show that the intrinsic impedance of the lossy medium is η = jωμ. σ+jωε Define reflection and transmission coefficient for normal incidence and write the formulae for E? Define Brewster angle? Obtain the expression for it? 0 Calculate the reflection coefficient for vertical polarization with oblique incident on perfect dielectric? Ensure the transmission for perfect conductor with normal incidence? UNIT-IV TRANSMISSION LINES- I Define a transmission line and explain the primary constants? 2 What is characteristic impedance? Obtain the relation between characteristic impedance and the propagation constant? 2 Define lossless and distortion less transmission lines and write the conditions for both? 4 Obtain the input impedance of a transmission line of length l characterized by Z 0 and γ. 4 UNIT-V TRANSMISSION LINES- II Derive the expression z 0 = Z oc Z sc. 2 Explain how an open circuit line acts as a circuit element? Explain how a short circuit line acts as a circuit element? 4 Explain the construction of smith chart?. Group - III (Analytical Questions) S.No QUESTIONS Program UNIT-I ELECTROSTATICS If T = (2 cos θ a r r + sin θ a θ ) A/m 2, calculate the current passing through a P a g e

9 S.No QUESTIONS hemisphere shell of radius 20 cm, 0 < θ < π 2, 0 < < 2π Program 2 Given that D = zρ cos 2 a z C/m 2, calculate the charge density at (, π 4, ) and the total charge enclosed by cylinder of radius m with 2 z 2m UNIT-II MAGNETOSTATICS A circular loop located on x 2 + y 2 =, z = 0 carries a direct current of 0A along a. Determine H at (0, 0, 4) and (0, 0, -4)? 2 Given the magnetic field vector potential A = ρ2 4 z Wb/m, calculate the total magnetic flux crossing the surface = π, ρ 2m, 0 z m? 2 A parallel plate capacitor with a plate area of cm 2 and plate separation of mm has a voltage 0 sin 0 t V applied to its plates. Calculate displacement current assuming = 2 0? UNIT-III EM WAVE CHARACTERISTICS In a lossless dielectric for which η= 0π, μ r = and H = 0. cos(ωt z)a x + 0. sin(ωt z)a y A/m. Calculate ε r, ω and E. 2 In a non magnetic medium E = 4 sin(2π 0 t 0.x)a z V/m. Findε r, η and time average power carried by the wave? A plane wave propagating through a medium with ε r =, μ r = 2 hase = 0.e z sin(0 t βz)a x. Determine the loss tangent, H field and intrinsic impedance. 4 In free space, H = 0.2 cos(ωt βx)a z A/m. Find the total power passing through a square plate of side 0cm on plane x + y = and a circular disk of radius cm on planex =. 2 A plane wave propagating through in a non magnetic medium has E = 0 sin(0 t + 2z)a y V/m. Find λ, ε r and H? In a free space(z 0), a plane wave with H = 0 cos(0 t βz)a x A/m is incident normally on a lossless medium (ε = 2ε 0, μ = μ 0 ) in regionz 0. For a copper coaxial cable shown below, let a= 2mm, b= mm and t=mm. Calculate the resistance of a 2m length of the cable at dc and at 00 MHz? Given a uniform plane wave in air as E = 40 cos(ωt βz)a x + 0 sin(ωt βz)a y V/m. Find Hi, and if the wave encounters a perfectly conducting plate normal to the z- axis at z=0, find the reflected wave Er and Hr. 2 2 UNIT-IV TRANSMISSION LINES - I An air line has a characteristic impedance of 0Ω and phase constant of rad/m at 00 Mhz. Calculate R, C and L. 2 A transmission line operating at 00 MHz has Z 0=0Ω, α=0.04 Np/m, β=. rad/m. Find line parameters R, L, G and C? A distortion less line has Z 0=0Ω, α=0.04 Np/m, u=0.c, where c is the speed of the light in a vacuum. Find R, L and G? 4 P a g e

10 S.No QUESTIONS 4 A telephone line has R= 0Ω/km, L= 00mH/km, G= 0 and C=20μF/km. at f= KHz obtain Z 0, γ and phase velocity (u). Program UNIT-V TRANSMISSION LINES II A certain transmission line 2m long operating at ω=0 rad/s has α=db/m, β=rad/m and Z 0=0+j40Ω. If the line is connected to a source of V, Z g= 40Ω and terminated by a load of 20+j0Ω. Determine the input Impedance and the sending end current 2 A lossless transmission line with Z 0=0Ω is 0m long and operates at 2MHz. the line is terminated with a load Z L= 0+j40Ω, if u=0.c on the line. Find the reflection coefficient Γ, standing wave ratio S and the input impedance Z in A load of 00+j0Ω is connected to a Ω lossless line. Find Γ, S and load admittance Y L A certain transmission line 2m long operating at ω=0 rad/s has α=db/m, β=rad/m and Z 0=0+j40Ω. If the line is connected to a source of V, Z g= 40Ω and terminated by a load of 20+j0Ω. Determine the input Impedance and the sending end current 0 P a g e