M GROUP Electromagnetic Theory
1.State Coulombs law. The force of attraction or repulsion between any two point charges is directly proportional to the product of the two charges and inversely proportional to the square of the distance between them 2.stata Gauss law. The electric flux passing through any closed surface is equal to the total charge enclosed by that surface 3.Define electric dipole. Two equal and opposite point charges separated by very small distance. 4.Define dipole moment. The product of electric charge and distance is known as dipole moment 5.Define electric flux. The lines of electric force is electric flux 6.Define electric flux density. It is defined as the electric flux per unit area. 7.Define electric field intensity. It is defined as the electric force per unit positive charge. 8.Name a few applications of gauss law in electrostatics. To determine the electric field intensity from a closed surface. 9.What is a point charge? Point charge is one whose maximum dimension is very small in comparison with any other length 10.Define potential Potential at any point is defined as the work done in moving a unit positive charge from infinity to that point in an electric field. 11.Define potential difference Potential difference is defined as the work done in moving a unit positive charge from one point to another point in an electric field. 12.Define current density. Current density is defined as the current per unit area.
13.What is meant by displacement current? Displacement current is nothing but the current that flows through the capacitor. 14.define conservative field. Any field where the closed line integral of the field is zero is said tobe a conservative field. 15.Write poisons equation ▼2v =-ρ/ε 16.Write laplaces equation ▼2v =0 17.What ia meant by a capacitor.? A capacitor is a electric device which consists of two conductors separated by a dielectric medium. 18.Defrine capacitance. The capacitance of two conducting planes is defined as the ratio of magnitude of charge on either conductor to the potential difference between the conductors. 19.Define electric field. It is the region of space where the charged body experiences a force. 20.Define electric flux density. It is defined as the number of flux lines passing through unit area. 21.State two properties of electric flux lines. i )these are imaginary lines of force having direction. ii)the line starts ata positive charge and and terminate on negative charge. 22.Give the relation between electric field intensity and potential gradient. E = - ▼v 23.Define potential gradient. It is the rate of charge of electric potential with respect to displacement. 24.Define permittivity Permittivity of a medium is defined as the ratio of D to E 25.Distinguish between absolute potential and relative potential. Absolute potential at any point is the potential at that point with respect to infinity. Relative potential is the potential at one point with respect to another point.
26.State divergence theorem. The integral of divergence of a vector field over a volume equals the surface integral of the normal component of electric flux density vector over the surface. 27.State stokes theorem. The line integral of a vector around a close d path is equal to the surface integral of the normal component of its curl over any surface bounded by the path 28.State amperes circuital law. Magnetic field intensity around a closed path is equal to the current enclosed by the path. 29.State Biot-savarts law. It states that the magnetic flux density at any point due to current element is proportional to the current element and sine of the angle between the elemental length and line joining and inversely proportional to the square of the distance between them. 30.Distinguish between diamagnetic, paramagnetic and ferromagnetic materials. In diamagnetic materials magnetization is opposed to the applied field. In paramagnetic materials magnetization is in the same direction as the field. It has weak magnetic field. In ferromagnetic materials magnetization is in the same direction as the field. It has strong magnetic field. 31.Define magnetic flux density. It is defined as the magnetic flux per unit area. 32.What is the relation between magnetic flux density and magnetic field intensity? B = µH 33.Write down the magnetic boundary conditions. 1)The normal component of flux density B is continuous across the boundary 2)The tangential component of field intensity H is continuous across the boundary. 34.Give the force on a current element. dF = BIdlsinθ 35.Define magnetic dipole. A small bar magnet with pole strength Qm and length l may be treated as magnetic dipole whose magnetic moment is Qml
36.Define magnetization. Magnetisation isdefined as the ratio of magnetic dipole moment to unit volume. 37.Define magnetic suspectibility It is defined as the ratio of magnetization to the magnetic field intensity. 38.What are the different types of magnetic materials. Diamagnetic Paramagnetic Ferromagnetic. 39.Give the formula for H inside a long current carrying solenoid. H = NI/l 40. Give the formula for Hat the centre of a circular current carrying coil H = NI/2r 41. Give the formula for H due to a infinite linear conductor H = I/2πh 42.Define conduction current Conduction current is defined as the current due to the movement of free electrons which are abundantly present in metallic conductors. 43.State faradays laws of electromagnetic induction. Faradays law states that electromagnetic force induced in a circuit is equal to the rate of change of magnetic flux linking the circuit 44.Give the expression for energy stored in a magnetic field. W = ½ LI2 45.Give the expression for energy stored in electric field. W = ½ CV2 46.Give the expression for energy density in electrostatic field. W=½ εE2 47.Give the expression for energy density in magnetostatic field. W =½µH2 48.Give the formula for inductance of a solenoid. L= µN2A/L 49.Give the formula for capacitance of a parallel plate capacitof. C = εA/d
50.Define a wave? If a physical phenomena that occurs at one place at a given time is reproduced at oter places at later times, the time delay being proportional to the space separation from the first location then the group of phenomena constitutes a wave. 51.Mention the propertiesof uniform plane waves. 1)At every point in space the electric field e and Magnetic field h are perpendicular to each other and to the direction of travel. 2)The fields vary harmonically with time and at the same frequency everywhere in space. 3)Each field has the same direction magnitude and phase at every point in any plane perpendicular to the direction of travel. 52.Define intrinsic impedance. It is the ratio of electric field to magnetic field or It is the ratio of square root of permeability to permittivity of the medium. 53.Define propagation constant. γ=α+jβ 54.Define skin depth Skin depth or depth of penetration is defined as that depth in which the wave has been attenuated to 1/e or approximately 37% of its original value. 55.Define pointing vector. P = EXH 56.State pointing theorem. The vector product of electric field intensity and magnetic field intensity at any point is a measure of rhe rate of energy flow per unit area at that point. 57.Give the expression for inductance of a solenoid. L = µN2A/l 58.Give the expression for inductance of a toroid. L = µN2R2/2R 59.Distinguish between transformer emf and motional emf The emf induced in a stationary conductor due to the change in flux linked with it is called transformer emf The emf induced due to the movement of conductor in a magnetic field is called motional emf
60.State Lenz’s law. Lenz’s law states that the induced emf in a circuit produces a current which opposes the change in magnetic flux producing it. 61.Give the formula for conduction current density and displacement current density Jc = σE Jd = εdD/dt 62.Express differential volume in Cartesian coordinate system. dv =dxdydz 63. Express differential volume in Cylindrical coordinate system dv = rdrdφdz 64. Express differential volume in spherical coordinate system dv = r2sinθdrdθdφ 65.Give the formula for conversion of Cartesian coordinate to cylindrical coordinate. r=√x2+y2 φ=tan-1(y/x) Z=Z 66.Give the formula for conversion of Cylinderical coordinate to cartesian coordinate X=rcosθ y=rsinφ z=z 67.What is the physical significance of gradient.? Gradient of a scalarfunction gives space variation of thatn function 68.What is the physicalsignificance of divergence? Divergence of flux density gives net outflow of flux per unit volume 69.What is the physical significance of curl of a vector field? Curl gives rate of rotation .CurlF gives work done per unit area. 70.Define linear charge density? It is defined as charge per unit length
71.Define surface charge density? It is defined as charge per unit area. 72.Define volume charge density.? It is defined as charge per unit volume. 73.Define electric field intensity? It is defined as the force per unit charge. 74.Define electrostatic force. The force between any two particles due to existing charges is known as electrostatic force. 75.Define polarization of dielectric material. Polarization is defined as the dipole moment per unit volume. 76.Sate the boundary condition at the interface between any two dielectric. 1)The tangential component of electric field is continuous. 2)The normal component of electric flux density is continuous. 77.State gauss law for magnetic field. The total magnetic flux passing through any closed surface is equal to zero. 78.Give the force on a current element. df = BIdlsinθ 79.Write the expression for magnetic field at the centre of a circular coil. H = I/2a 80.Define magnetic moment. m=IA 81.Define solenoid Solenoid is a cylindricalshaped coil of a large number of closely spaced turns of insulated wire wound usually on a non magnetic frame. 82.Dfine Toroid. A solenoid bent in the form of a ring forms a toroid. 83.Give the characteristic impedance of free space. 377Ω
84.Define self inductance. self inductance is the rate of magnetic flux linkage to the circuit through the coil . 85.Define mutual inductance. The mutual inductance between two coils is defined as the rate of induced magnetic flux linkage in one coil to the current flowing in other coil. 86.Define reluctance. Ratio of mmf to magnetic flux. 87.What is Brewster angle.. Brewster angle is a particular angler at which no reflection takes place. 88.Slefine slepian vector .Slepian vector is defined at any point such that its flux out of any volume is zero 89.Give the expression for force per metre length between two parallel conductors. F = µI1I2/2πd 90.What are the conditions for two vectors to be parallel AXB = 0 91.What are the conditions for two vectors to be perpendicular? A.B =0 92.Give the significance of continuity equation. Since the charge is conserved,the outward flux of J must therefore be equal to the rate of loss of charge within the volume. 93.Define magnetic vector potential. A = µ/4π ⌠⌠⌠Jdv/r 94.Define coefficient of coupling. The fraction of total flux produced by one coil linking a second coil is called coefficient of coupling. K =M / √L1L2 95.Give the expression for inductance per unit length of a coaxial transmission line. L = µ/2πln(b/a)
96.define linear polarization. If x and y component of electric field Ex and Ey are present and are in phase the resultant electric field has a direction at an angle of tan-1Ey/Ex and if this angle is constant with time the wave is said to be linearly polarized. 97. Define circular polarization. If x and y component of electric field Ex and Ey have equal amplitude and 90 phase difference the locus of the resultant electric field is a circle and the wave is said to be circularly polarized 98. Define Elliptical polarization. If x and y component of electric field Ex and Ey have different amplitude and 90 phase difference the locus of the resultant electric field is a ellipse and the wave is said to be elliptically polarized 99. define permeance Permeance is the reciprocal of reluctance. 100.Give the expression for magnetic flux density at the centre of a toroidal coil. H = NI/2πr 16 marks questions 1.Derive an expression for electric field due to an infinite long charge. 2.Derive expression for electric field intensity due to a dipole. 3. Derive expression for potential due to a dipole. 4.derive expression for energy and energy density in a electric field. 5.Derive an expression for capacitance between two parallel wires. 6.derive an expression for magnetic field intensity due to an infinite long current carrying conductor. 7. derive an expression for magnetic field intensity at any point on the axis of a circular coil carrying current. 8.Derive an expression for magnetic vector potential 9.Derive the magnetic boundary conditions. 10. Derive an expression for magnetic field intensity on the axis of a solenoid. 11.State and prove divergence theorem? 12. State and prove stokes theorem? 13explain the relationship between Cartesian and cylindrical and Cartesian and spherical. 14.Use the cylindrical coordinate system to find the area of the curved surface of a right circular cylinder where r =20m, h =5m, 30°≤φ≤120°.
15.Explain spherical coordinate system and differential elements in spherical coordinate system. 16.Derive the relation between field theory and circuit theory for an RLC series circuit. 17.Deive all the four maxwells equations. 18.State and explain faradays law of electromagnetic induction. 19.Briefly expain Displacement and conduction current. 20.Derive the wave equations. 21.State and explain poyntings theorem. 22.Derive the expressions describing propagation of uniform plane waves in good conductor. 23.Explain reflection of uniform plane waves with normal incidence at a plane dielectric boundary. 24.Define transmission coefficient and reflection coefficient. What is the relationship between them. 25.Derive the expression for average poynting vector