# Electromagnetics and Field Theory Part One

**Instructions:** Click the answer button to see the correct answer.

- Two parallel plates are separated by a distance D charged by V volt. The field intensity E is given by,
- V / D
- V²/ D
- V × D²
- V × D

Answera

- As

a result of reflection from a plane conducting wall, electromagnetic

waves acquire an apparent velocity greater than the velocity of light in

space. This is called the- normal velocity.
- phase velocity.
- group velocity.
- velocity of propagation.

Answerb

- Inside a hollow conducting sphere
- electric field changes with distance from the center of the sphere.
- electric field is zero.
- electric field changes with magnitude of the charge given to the conductor.
- electric field is a non zero constant.

Answerb

- Electric field intensity (E) at ant point in an electric field is equal to
- (potential gradient)⅓.
- (potential gradient)².
- √(potential gradient).
- potential gradient.

Answerd

- An

electric field on a place described by its potential V = 20(r⁻¹ + r⁻² )

where r is the distance from the source. The field is due to- A dipole.
- Both A dipole & A monopole
- A monopole.
- A quardra pole.

Answerb

- Two

point charges are in the vertex of the square. If potential is another

vertex is 2 V, so potential in opposite vertex (diagonally) is- 2 V.
- √ 2 V.
- 1 V.
- Zero.

Answera

- A

metal sphere with 1 m radius and a surface charge density of 10

coulombs / m² is enclosed in a cube of 10 m side. The toatal outward

electric displacement normal to the surface of the cube is.- 5 C.
- 10 C.
- None of these
- 40π C.

Answerd

- An

electric dipole of moment P is placed in front of a ground sphere. The

change induced on the surface of the sphere is (Assume radius of sphere =

R and distance from dipole to centre of sphere = d)- PR/d.
- Zero.
- PR²/d³.
- PR/d².

Answerd

- What is the value of total electric flux coming out of a closed surface?
- Equal to the surface charge density.
- Equal to total charge enclosed by the surface.
- Equal to volume change density.
- Zero.

Answerb

- Electric field strength of charge
- Decrease with square distance.
- Decrease with distance.
- Increase distance.
- Increase square distance.

Answera

- The statement which is not correct from the following:
- An electric flux line is an imaginary path or a line drawn in such a

way, that its direction at any point is the direction of electric field

at that point. - Gauss’s law static that total electric flux through any surface is equal to the total charge enclosed by surface.
- Gauss’s static that divergence of D = ρu.
- For a uniform long charged line with l1 c/m the electric field intensity E is given as E = ρL/(π ε₀.r).

Answerd

- An electric flux line is an imaginary path or a line drawn in such a
- Two infinite parallel metal plates are charged with equal surface charge density of the same plates is.
- Double of field produced by one plate.
- Dependent on coordinates of field point.
- The same as that produced by one plate.
- Zero.

Answerd

- An insulated metal sphere of 20 cm diameter is charged by rubbing with charges 2 × 10⁻⁸ C. Potential developed will be
- 2.88 V.
- 28.8 V.
- 14.40 V.
- 1.4 V.

Answerb

- Which of the following statement are incorrect?
- A dielectric material is liner if ε does not change with applied field.
- In a liner dielectric P varies linearly with E.
- A dielectric material is isotropic if &elipson; does not change with direction.
- A conductor is an equipotential body and E is always tangential to the conductor.

Answerd

- Between a hollow and solid metal sphere, charge reside
- On outer surface in both.
- On outer surface in solid and throughout hollow.
- On outer surface in hollow and throughout is solid.
- None of above.

Answera

- The electric flux is given D = (2y² + z) Ix + 4xy Iy + x 1z C/m². The volume charge density at point (-1,0,3) is
- – 2 C/m³.
- – 8 C/m³.
- 0 C/m³.
- – 4 C/m³.

Answerd

- Gradient of scalar field is expressed as
- Circulation of a vector field per unit area as the area tends to zero.
- Outward flux of a vector field per unit volume as the volume about the point tends to zero.
- Gradient of divergence of a vector field minus the curl of the vector field.
- Maximum rate of increase of scalar function at appoint.

Answerd

- A vector field A = p 1 n is given in Cartesian coordinates. In cylindrical coordinates it will be represented as
- A = cosφ 1r + sinφ Iφ.
- A = sinφ 1r.
- A = cosφ 1r – sinφ 1r.
- A = cosφ 1r.

Answerc

- A potential field is given by V = 3x²y –yz. The electric field at P(2, -1, 4) is
- 12 1x – 8 1y V/m.
- 12 1x – 1z V/m.
- 12 1x – 8 1y – 1z V/m.
- 12 1x + 8 1y + 1z V/m.

Answerc

- A sphere of radius with a uniform charge density ρv C/m³ shall have electric flux density at the radius r = a equal to
- aρ C/m².
- ρ/3 C/m².
- aρv/4 C/m².
- aρ/3 C/m².

Answerd

- An infinite sheet has a charge density of 150 μ C/m. The flux density in μ C/m² is
- 1/75.
- 75.
- 50.
- 100.

Answerb

- If

in a 1 mF capacitor, an instantaneous displacement current of 1 A is to

be established in the spaces between its plates then it is possible by- 10⁶ Amp/see.
- 10⁶ volts/see.
- 10⁶ volts.
- 10⁶ Amp.

Answerb

- The work done by a force = 4un – 3uy + 2uz N in giving a inc charge a displacement of (10 ux + 2uy – 7uz) m is
- 100 nj.
- 40 nj.
- 20 nj.
- 60 nj.

Answerc

- Which statement does not say that electrostatic field conservative?
- If is gradient of a scalar potential.
- The work done in a closed path inside the fields is zero.
- If the curl of E is identically zero.
- The potential difference between two points is zero.

Answerd

- A

circular ring carrying uniformly distributed charge q and a point

charge – Q on the axis of the ring. The magnitude of dipolement of the

charge system is (Assume distance between centre of ring and point

charge is d and radius of ring R)- QR.
- Q√(R⁶ + d⁶).
- QD.
- QR⁶/d.

Answerc

- If E is the electric field intensity, then what is the value of divergence of (curl of E)?.
- Null vector.
- Zero.
- E.
- | E |.

Answerb

- A

sphere of zoo radius contains electrical charge of density 2/(r sinθ)

c/m³. What is the total charge contained within the sphere?- 0.
- None of these.
- 0.335/sinθ c.
- 0.335 C.

Answerc

- Two sphere of radius r1 and r2 are connected by a conducting wire. Each of the spheres has been given a charge Q. Now
- Both of sphere will have same potential.
- Larger sphere will have greater potential.
- Larger sphere will have smalled potential.
- Smaller sphere will have zero potential.

Answera

- In frec space E (z,t) = 10³ sin(ωt – βz) uy v/m. What is the value of H (z,t)
- (10³/377) sin(ωt – β z)(-uy) A/m.
- (10³/377) sin(ωt – β z)(-ux) A/m.
- None of these
- (10³/377) cos(ωt – β z)(-ux) A/m.

Answera

- n a lossless medium the intrinsic impedance η 60π and μr = 1. The relative dielectric constant εr shall be
- 8.
- 4.
- 1.
- 2.

Answerb

- A plane wave magnetic field is represented by Bx = cos(y – ct). The electric and magnetic fields will be zero in the direction
- Ex = Ey = 0, By = Bz = 0.
- Ey = Ez = 0, By = Bz = 0.
- None of these.
- Ex = Ey = 0, Bx = By = 0.

Answerd

- What is the value of skin depth as 100 Hz in a material having μr = 1.0 and &sigma = 3.60 × 10⁷ s/m
- 4 mm.
- 2.4 mm.
- 10 mm
- 8.4 mm.

Answerd

- kin depth is proportional to
- Frequency.
- √(σ).
- Permeability.
- 1/√σ.

Answerd

- If n is the polarization vector and k is the direction of propagation plane electromagnetic wave, them
- n × k =0.
- n = K.
- n = – k.
- n.k =0.

Answera

- A

solid sphere made of insulating material has a radius R and has a total

charge Q distributed uniformly in its volume. What is the magnitude of

electric field intensity, E, at a distance r (o less than r less than R)

inside the sphere- 3 Qr/(4 π εo R³).
- Q/(4 π εo r³).
- QR/(4π εo r³)
- Qr/(4 π εo R³).

Answera

- For a line characteristic impedance zo terminated is load zo/3, the reflection coefficient is
- 1/3.
- – ½.
- 2/3.
- – 1/3.

Answerb

- Find H for centre of solenoid having finite length d = 1 unit where N = no of turns = 500, 1 = 2 A.
- None of these
- 1000.
- 500.
- 100.

Answerb

- A magnetic vector potential is given by the expression A = (- cos x) (cos y) uz. The flux density at the origin is
- – 2 ux.
- 2 ux.
- – uy.
- 0.

Answerd

- The Kirchhoff’s current law is implict in expression
- Curl of H = J + (δ D)/(δ t).
- Surface integral of (j.ds) = 0.
- Divergence of B = 0.
- Divergence of D = ρv.

Answerb

- A

rectangular loop in the x – z plane bounded by the lines x=o, x=a, z=o

and z=b is in a time varying magnetic field is given by B=Bo cosω + ay.

Where Bo is constant, ω is angular frequency and ay unit vector in the y

direction. Now the emf induced in the loop is given- Bo ω sinω t.
- ab Bo cosω t.
- abω Bo sinω t.
- Zero.

Answerc

- The

force on a charge moving with velocity v under the influence of

electric and magnetic fields is given by which one of the following- q(E + V) × B).
- q(H + V × E).
- q(E + B × V).
- q(E +V × H).

Answera

- Which is the major factor for determining whether a medium is free space, lossless dielectric or a good conductor
- Loss tangent.
- Reflector coefficient.
- Constitutive parameters.
- Attenuation constant.

Answera

- If the static magnetic flux density is B, then
- Curl of B = J.
- Curl of B = 0.
- Divergence of B = J.
- Divergence of B = 0.

Answerd

- Which of the following statement for a divergence of electric and magnetic flux densities
- It is zero for the electric flux density.
- These are zero for static densities but non zero for time varying densities.
- It is zero for the magnetic flux density.
- Both are zero.

Answerc

- Poyniting vector has the dimensions
- none of these
- Watts/metre².
- Wall/metre².
- Watt/metre.

Answerb

- For a linear electromagnetic circuit, which of the following statement is true?
- Field energy is lesser than the co-energy.
- Field energy is greater than the co-energy.
- Co-energy is zero.
- Field energy is equal to the co-energy.

Answerd

- A conductor is rotating with in a magnetic field. At which of the positions do the peak voltages occur?
- Anywhere.
- At 45 Â° angles to the axis of the magnetic field.
- Along the axis of the magnetic field.
- At right angles to the axis of the magnetic field.

Answerc

- The electric field intensity of an equipotential surface is
- always perpendicular to the surface
- zero
- None of these.
- always parallel to the surface

Answerb

- he surface integral of electric field intensity gives
- flux density
- net charge enclosed by the surface
- None of these
- net flux imanating out from the surface

Answerb

- An

average emf of 10 V is induced in a 100 turn solenoid as a result of a

change in flux which occurs in 0.5 second. The total flux change is- 5
- 0.5
- 0.05
- 5

Answerc

Copyright (C) 2016 by Charles Kelly (ALL EXAM REVIEW ADDA)