61. A line with lumped parameters of series resistance 10 Ω shunt resistance is composed of 200 Ω. 10 T sections matched to a generator with an emf of 3 volts and terminated by its characteristic impedance. The current at the sending end of the line is—

1. 1. 24.4 µA

   
   
   

   2. 0.066 A

   
   
   

   3. 0.033 A

   
   
   

   4. 0.0033 A

   
   
   

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1. View Hint View Answer Discuss in Forum

   A line having the T or π sections in transmission line have the same characteristic impedance after many sections addition and characteristic impedance may be found by image impedance
   Z₀ = √Z₁.Z₂
   

   =	√	Z1Z2 +	Z21
   			4

   
   here
   
   

   Z0 =	√	10 × 200 +	(10)2	= 45 Ω
   			4

   
   Now we have simplified diagram
   
   So we give as current through input terminal as
   

   3V	=	3V	=	6	= 0.066A
   Z0		45		45

   Correct Option: B

   A line having the T or π sections in transmission line have the same characteristic impedance after many sections addition and characteristic impedance may be found by image impedance
   Z₀ = √Z₁.Z₂
   

   =	√	Z1Z2 +	Z21
   			4

   
   here
   
   

   Z0 =	√	10 × 200 +	(10)2	= 45 Ω
   			4

   
   Now we have simplified diagram
   
   So we give as current through input terminal as
   

   3V	=	3V	=	6	= 0.066A
   Z0		45		45

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62. The shortest stub length in λ required to produce a reactance equal to Z₀is—

1. 1. λ

   
   
   

   2. λ

      8

   
   
   

   3. λ

      4

   
   
   

   4. 2 λ

   
   
   

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1. View Hint View Answer Discuss in Forum

   Refer synopsis

   Correct Option: B

   Refer synopsis

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63. Input impedance for the given line is—
    

1. 1. Inductance

   
   
   

   2. Capacitance

   
   
   

   3. Tank circuit

   
   
   

   4. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   Graph shows clearly that shorted stub of given length is of capacitive type.

   Correct Option: B

   Graph shows clearly that shorted stub of given length is of capacitive type.

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64. A beam antenna consists of a dipole one reflector and one director. The velocity factor is 0.90 and antenna is to be cut for a frequency of 150 MHz. The length of the dipole will be—

1. 1. 0.4 m

   
   
   

   2. 0.5 m

   
   
   

   3. 0.9 m

   
   
   

   4. 1.2 m

   
   
   

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1. View Hint View Answer Discuss in Forum

   By calculation as follows
   

   λ =	C
   	velocity factor × f

   
   

   λ =	3 ×108
   	0.9 × 150 × 106

   
   = 1.8
   

   Now effective length of dipole =	1	⇒	1.8	= 0.9
   	2		2

   Correct Option: C

   By calculation as follows
   

   λ =	C
   	velocity factor × f

   
   

   λ =	3 ×108
   	0.9 × 150 × 106

   
   = 1.8
   

   Now effective length of dipole =	1	⇒	1.8	= 0.9
   	2		2

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65. For a short wave radio link between two stations via the ionosphere. The ratio of the maximum usable frequency to the critical frequency—

1. 1. Is always less than 1

   
   
   

   2. Is always greater than 1

   
   
   

   3. May be less than or more than 1 depending on the distance between the two stations

   
   
   

   4. Does not depend on the distance between the two stations
      

   
   
   

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1. View Hint View Answer Discuss in Forum

   Since we know that f_muf = f_c sec i
   so,
   

   fmuf	= sec i > 1
   fc

   
   

   Correct Option: B

   Since we know that f_muf = f_c sec i
   so,
   

   fmuf	= sec i > 1
   fc

   
   

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