# JNTU II B.Tech I Semester Regular Examinations, November 2008

JNTU II B.Tech I Semester Regular Examinations, November 2008

ELECTROMAGNETIC WAVES AND TRANSMISSION LINES

(Electronics & Instrumentation Engineering)

SET-3

1. (a) An infinite line charge, ?L = 10 nC/m parallel to z-axis is at x = 3, y = 4 in

free space. Find E at (a) (0, 0, 0), (b) (0, 1, 2), (c) (1, 1, 1).

(b) A parallel plate capacitor with free space between the plates remains connected

to a constant voltage source while the plates are moved closer together from separation d to ?d. Find the charge in ?s , C, D, E.

2. (a) Derive Amperes circuit law in differential form.

(b) What is the magnetic field, H in Cartesian coordinates due to z-directed current element and hence find out J if I = 2 A.

3. (a) Prove that the field given by E = x2ax + x ay can not arise from a static distribution of charge.

(b) Show that the power density corresponding to the field E = ax cos (?z ? ?t) + ay sin (?z ? ?t) is constant everywhere.

4. (a) Identify frequency, phase constant when the electric field of an EM wave is

given by E = 5.0 sin(108t – 4.0x)az. Also find ?.

(b) Describe the propagation characteristics of EM waves in good dielectrics.

5. (a) Explain the characteristics of Uniform plane wave in perfect dielectric?

(b) A 300MHz uniform plane wave propagates through fresh water for which ? =0, ?r = 1, ?r = 78. Calculate:

i. The attenuation constant

ii. The phase constant

iii. Wavelength

iv. Intrinsic impedance.

6. (a) Explain the different excitation methods for different TE and TM waves.

(b) A rectangular waveguide with dimensions 3 × 2cm operates at 10GHz. Find fc, ?c, ?, ?g, ?g, ?p of TE10 mode.

7. Derive the equation for input impedance of a transmission line. & deduce the expression for short & open circuited lines.

8. (a) Explain applications of the smith chart?

(b) A lossless transmission line of length 100m has an inductance of 28?H and a capacitance of 20nF. Find propagation velocity, phase constant at an operating

frequency of 100kHz and characteristic impedance of the line.