Tuesday, September 1, 2020

Chapter 3 : Electromagnetism- Page 10

Chapter 3 : Electromagnetism

91. The input impedance of a loss-less transmission line is 100 ohms when terminated in a short-circuit, and 64 ohms when terminated in an open circuit. The characteristic impedance of the line is

 
A. 36 ohms
B. 64 ohms
C. 80 ohms
D. 164 ohms


... Answer is ( C)

 

 
 

92. Which one of the 'following sets of equations is independent in Maxwell's equations?

 
A. Both the curl and divergence auditions
B. The two curl equations combined with the continuity equation.
C. The two curl equations
D. The two divergence equations

... Answer is (A)

 
 
 

93. Two conducting shells of radii rt and r2 (r1 > r2), each with a charge 'Q' ar placed for apart in a uniform external electric field. The space surrounding each shell is filled with the same dielectric material.In this situation, the

A. shell with radius r1 will experience a greater force
B. shell with radius r2 will experience a greater force

C.
shells will not experience any force
D. shells will experience identical forces

... Answer is (D)

 

 
 

94. A transmission line of characteristic impedance Zo = 50 ohms, phase velocity v = 2 x 10⁸m/s, and length I = 1 m is terminated by a load 11(30 - j 40) ohms. The input impedance of the line for a frequency of 100 MHz will be

 
A. (30 + j40) ohms
B. (30 - 40) ohms
C. (50 + j40) ohms
D. (50 - j40) ohms

  ... Answer is (B)

 

 
 
95. The Fleming's left hand rule correlates to
  ...
Answer is (B)

 
 
 

96. The unit of relative permeability is
A.
henry/metre
B. henry
C. henry/sq.m
D. it is dimensionless

  ... Answer is (D)

 

 
 

97. The force between two long parallel conductors is inversely proportional to

A. product of current in two conductors
B. distance between the conductors

C.
radius of conductors
D. current in one conductor

... Answer is (B)

 
 

98.. Materials subjected to rapid reversal magnetism should have

A. large area of B-H loop
B. high permeability and low hysteresis
C. high co-ercivity and high retentivity loss
D. high co-ercivity and low density

... Answer is (B)

 
 

99. Indicate which of the following material does not retain magnetism permanently.

A. Hardened steel
B. Soft iron
C. Stainless steel
D. None of the above
 
  ... Answer is (B)

 
 

100.  The main constituent of perm-alloy is


A.
cobalt
B. chromium
C. nickel
D. tungsten

  ... Answer is (C)

 

 

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