Electricity and Magnetism Answers

5. a) Explain the time division multiplexing used in telephony.
b) Explain the sub-carrier multiplexing (SCM) scheme used in optical communication.
Why should it be used in conjunction with WDM?

4. a) Compare the performance of the four types of AM generators discussed in the study
material.
b) What is pulse time modulation? Explain the ways to obtain different forms of PTM
signals from an analog signal.

3. a) Explain the difference between analog bandwidth and digital bandwidth in
communication systems.

2. a) Explain the measures you will take to protect the signal from (i) electromagnetic
interference, (ii) partition noise and (iii) fading effects.

1. State with reasons whether the following statements are True or False.
i) Sound and light waves are the only two ways of establishing a communication link.
ii) More number of bits will be required to transmit a signal using Hindi language
alphabets than using English language alphabets.
iii) In a standing wave pattern the distance between the two maxima is equal to the
wavelength of the incident wave.
iv) It is advisable to have the highest value of the amplitude modulation index.
v) Frequency shift keying is modulation of digital carrier signal with an analog intelligent
signal.
vi) Mobile telephony cannot handle analog signal.
vii) Colour television signal can be obtained by using black and white cameras.
viii) Only visible band signals can be transmitted through an optical fibre.
ix) Share level security provides stronger protection than user level security in a
network.
x) WAP helps in connecting devices without cables.

Using Maxwell’s equations in free space, derive the wave equation for the
electric field vector. Obtain the conditions under which the following time varying
electric and magnetic fields satisfy Maxwell’s equations in vacuum with no source
charges or currents:
E = k^ E0 sin ( y- vt )
B = i^ B0 sin (y − vt)
where E0 and B0 are constant.

I=√2sin(100πt-π⁄2),find frequency?

in an electric feild the potential at a point is given by following relation: V=343/r.
the electric feild at r=3i+2j+6k is

Using Maxwell’s equations in free space, derive the wave equation for the electric field vector. Obtain the conditions under which the following time varying electric and magnetic fields satisfy Maxwell’s equations in vacuum with no source charges or currents:
E = k^E0 sin( y − vt)
B = i^B0 sin( y − vt)
where E0 and B0 are constant.

Using Maxwell’s equations in free space, derive the wave equation for the
electric field vector. Obtain the conditions under which the following time varying
electric and magnetic fields satisfy Maxwell’s equations in vacuum with no source
charges or currents:
sin ( )
ˆ
0 E = k E y − vt
) sin (
ˆ
0 B = i B y − vt
where E0 and B0 are constant.