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ELEC 210

SECOND SEMESTER EXAMINATIONS 2021/22

ELECTROMAGNETICS

1.    a)    Explain what is meant by the following terms in electromagnetics:

i)      Electrical potential

ii)     Supercapacitor

iii)    Streamlines

b) A charge 30 nC is situated at the point (x, y, z) = (0, 1, 0) m and a charge of - 30 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 +10 nC charge at the point P (2, - 1, 2) m

c)    i)      State Gauss’s law for electric fields. Give the corresponding equation in differential or integral form explaining the significance and the units of each term used.

ii)     Using  Gauss’s  law  show  how  the  relationship  known  as  Laplace’s equation for charge free regions may be derived.

Total 32

2.    a)    Explain what is meant by the following terms in electromagnetics:

i)      Relative permeability

ii)     Voltage standing wave ratio

iii)   Drift velocity

b)   Starting with Maxwell’s equations in vacuum (no materials, no currents, no charges) derive the wave equation for the magnetic field.

c)    i)      Show that including the effect of the displacement current, the curl of B may be written as

ii)     Outline, briefly, how the introduction of the displacement current leads to the possibility of electromagnetic waves .

Total 32

3.    a)    i)      Explain the term Transmission Line in electromagnetics .

b)   i)      The force on a charged particle moving in an electric and magnetic field can be represented by the equation: