(d) A lossless transmission line is 330m long. The inductance (L, and capacitanc
ID: 1766275 • Letter: #
Question
(d) A lossless transmission line is 330m long. The inductance (L, and capacitance (C) are determined by measuring a 30m section of the line. The section is found to have an inductance of 0.25mH and a capacitance of 1100pF. Determine:- (3 marks) (3 marks) (e) Waveguides are hollow structures that are use to carry high (2 marks) i. The characteristic impedance of the line. ii. The velocity of the wave on the line. frequency radio waves. Based on your understanding of the phenomenon known as "skin effect", explain briefly why waveguides structures are hollow.Explanation / Answer
(d) For loss less transmission line
(i).Characteristic impedance=(L/C). Because attenuation coefficients are zero
Z0=(L/C=(0.25×10-3)/(1100×10-12)
Z0=(2.5/11)×106.
Z0=(0.227×106=0.476×103.
Finally characteristic impedance=Z0=476ohms.
(ii).velocity o wave on the line=V=1/(LC)=1/(0.25×10-3×1100×10-12)
V=1/(27.5×10-14)=1/(5.244×10-7)=0.2×107=2×106 m/s.
(e). Skin efect is the tendency of an alternating electric current (AC) to become distributed with in the conductor such that current density is largest near the surface of the conductor and decreases with greater depths in the conductor. Electric current flows mainly at the skin of the conductor between the outer surface and a level called the skin depth.
Skin effect causes effective resistance of the conductor to increase at high frequencies where skin depth us smaller,thus reducing effective cross section of the conductor.The skin effect is due to opposing eddy currents induced by changing magnetic field from the alternating current.
Due to this hollow conductor shape attenuation is less at higher radio frequencies using above definition of skin effect than transmission lines.That is why waveguide with hollow structures are using at higher radio frequencies for sending em waves.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.