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Electromagnetic Theory Mcqs

Q:

One end of a lossless transmission line having the characteristic impedance of 75 ohm and length of 1 cm is short circuited. At 3 GHz, the input impedance at the other end of the transmission line is

A) 0 B) Resistive
C) Inductive D) Capacitive
 
Answer & Explanation Answer: D) Capacitive

Explanation: Not available for this question

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100
Q:

The minimum distance of the stub from the load side is 5 cm. Calculate the guided wavelength of the transmission line.

A) 5 cm B) 2.5 cm
C) 10 cm D) 1.25 cm
 
Answer & Explanation Answer: C) 10 cm

Explanation: The minimum distance of the stub from the load line is given by Vmin = wavelength/2. On substituting the given value, we get the guided wavelength as 10 cm.

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50
Q:

The capacitance per unit length and the characteristic impedance of a lossless transmission line are C and Z respectively. The velocity of a travelling wave on the transmission line is

A) ZC B) 1/ZC
C) Z/C D) C/Z
 
Answer & Explanation Answer: B) 1/ZC

Explanation: The characteristic impedance of the Z = ?(L/C) and the velocity of propagation is V = 1/?(LC). Thus we get V = 1/ZC.

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82
Q:

A lossless line having 50 ohm characteristic impedance and length wavelength/4 is short circuited at one end connected to an ideal voltage source of 1V at the other end. The current drawn from the voltage sources is

A) 0 B) 0.02
C) Infinity D) 50
 
Answer & Explanation Answer: A) 0

Explanation: Not available for this question

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117
Q:

A transmission line is distortionless if

A) RL = 1/GC B) RL = GC
C) LG = RC D) RG = LC
 
Answer & Explanation Answer: C) LG = RC

Explanation: Condition for distortionless line is R/L = G/C. In other words, the rise time constant is equal to the fall time constant. Hence RC = LG.

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98
Q:

In an impedance Smith chart , a clockwise movement along a constant resistance circle gives rise to

A) Decrease in reactance B) Increase in reactance
C) No change in reactance D) No change in impedance
 
Answer & Explanation Answer: B) Increase in reactance

Explanation: In clockwise direction, along the constant resistance circle gives rise to an increase in the value of reactance.

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62
Q:

For maximum power transfer, a lossless transmission line 50 ohm is to be matched to a resistive load impedance of 100 ohm. The characteristic impedance of the wavelength/4 transformer is

A) 70.7 B) 50
C) 100 D) Infinity
 
Answer & Explanation Answer: A) 70.7

Explanation: Not available for this question

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76
Q:

For an electromagnetic wave incident from one medium to a second medium, total internal reflection takes place when

A) Angle of incidence is equal to the Brewster angle with E field perpendicular to the plane of incidence B) Angle of incidence is equal to the Brewster angle with E field parallel to the plane of incidence
C) Angle of incidence is equal to the critical angle with the wave moving from the denser to rarer medium D) Angle of incidence is equal to the critical angle with the wave moving from the rarer to denser medium
 
Answer & Explanation Answer: C) Angle of incidence is equal to the critical angle with the wave moving from the denser to rarer medium

Explanation: Total internal reflection takes place when the angle of incidence is greater than the critical angle. Also the wave should move from the denser medium to a rarer medium.

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