ELEC 210 ELECTROMAGNETICS SECOND SEMESTER EXAMINATIONS 2018-19
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ELEC 210
SECOND SEMESTER EXAMINATIONS 2018-19
ELECTROMAGNETICS
1. a) Explain what is meant by the following terms in electromagnetics:
ii) capacitor cell
iii) drift velocity
b) A charge of 60 nC is situated at the point (x, y, z) = (0, 1, 0) m and a charge of -60 nC at the point (0, -1, 0) m. Both charges are in free space. Determine:
i) the electric field at the point P (2, -1, 2) m .
ii) the electric flux density at the point P (2, -1, 2) m .
iii) the electric force on a +5 nC charge at the point P (2, -1, 2) m .
c) If the scalar electric potential V = 2x2y + 4z, find the electrical field.
d) A sphere of 2 m radius has a point charge of 8 nC at its centre. Find the electric flux passing through that part of the sphere between ± 60o latitude and ± 20o longitude.
Total 34
2. a) i) What is meant by the displacement current in electromagnetics?
ii) How does it influence the Ampere’s law for static magnetic field and the time varying electromagnetic field?
b) Explain the contrasting physical consequences of the equations:
VB = 0
· D = P
Using Gauss’s law, show how the relationship known as Laplace’s equation for charge free regions may be derived.
c) At a point P(x, y, z) in free space, the magnetic field is given by
B = 2 zay - 0.8 yaz (μT)
Find
i) the magnetic field intensity H at the point P.
ii) the electric current density J at the point P .
d) State the complete and the integral form of Faraday’s law defining each term used.
Total 34
3. a) Explain what is meant by the following terms in electromagnetics:
i) magnetic flux density
ii) transmission line
b) Discuss the factors related to the geometry of a circuit and the signal frequency which are useful to determine whether transmission line effects can be ignored or must be considered.
c) A signal of 20 V is applied to a 25 co-axial transmission line terminated in a 100 load. Calculate:
i) the voltage reflection co-efficient.
ii) the magnitude of the reflected voltage.
iii) the voltage standing wave ratio.
d) A two-wire air line has the following line parameters: resistance R = 0 .8 mΩ/m
admittance G = 2.1 mS/m, inductance L = 0.65 H/m, and capacitance C = 14 nF/m.
i) Determine the attenuation constant and the phase constant β at 1 kHz.
ii) Find the characteristic impedance Z of the line at 1 kHz.
iii) A loading ZL is connected to the two-wire air line. To have maximum power transmitted to the loading, what should the value of ZL be?
Total 32
2023-08-26