20634399
Descripción
Test por Owen Ryan Ang, actualizado hace más de 1 año
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Creado por Owen Ryan Ang
hace más de 4 años
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Pregunta 1
Pregunta
A natural magnet is called
Respuesta
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steel
-
lodestone
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magnetism
-
soft iron
Pregunta 2
Pregunta
A magnet is able to attract
Respuesta
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iron, aluminum and brass
-
iron, cobalt and zinc
-
iron, copper and nickel
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nickel, cobalt and steel
Pregunta 3
Pregunta
Externally, magnetic line of force travels
Respuesta
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south to north
-
north to south
-
negative to positive
-
in both directions
Pregunta 4
Pregunta
A material commonly used for shielding or screening magnetism is
Respuesta
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brass
-
aluminum
-
copper
-
soft iron
Pregunta 5
Pregunta
The magnetism that remains in a magnet after the magnetizing force has been removed is called
Respuesta
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permeability
-
induction
-
residual
-
saturation
Pregunta 6
Pregunta
Iron becomes magnetized by induction when it is
Respuesta
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heated
-
suspended east and west
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near to one end of a magnet
-
treated with some chemicals
Pregunta 7
Pregunta
Magnetic lines of force are called
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hysteresis
-
current
-
flux
-
magnetomotive force
Pregunta 8
Pregunta
The force between two magnetic poles varies with distance between them. The variation is
Respuesta
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in direct proportion to the distance
-
in inverse proportion to the distance
-
in direct proportion to the square of the distance
-
in inverse proportion to the square of the distance
Pregunta 9
Pregunta
The magnetic potential in a magnetic circuit can be measured in terms of
Respuesta
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farads
-
M.M.F.
-
coulombs
-
none of these
Pregunta 10
Pregunta
Permeance is analogous to
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conductance
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resistance
-
reluctance
-
none of these
Pregunta 11
Pregunta
The permeability of a material means
Respuesta
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strength of permanent magnet
-
strength of an electromagnet
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the magnetization left in the iron after exciting field has been removed
-
the conductivity of a material for magnetic lines of force
Pregunta 12
Pregunta
When magnetic flux (Φ) and the area (A) under its influence are known, the magnetic flux density (B) can be given as
Respuesta
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B = ΦA
-
B = Φ/A
-
B = A/Φ
-
B = ΦA2
Pregunta 13
Pregunta
The relative permeability μr is given by
Respuesta
-
B/μr0H
-
B/H
-
μ0/μ
-
μ0/H
Pregunta 14
Pregunta
Relative permeability of a material is given by (K is susceptibility of the material)
Respuesta
-
1 + μ0K
-
1 + K/μ0
-
1 + μ0/K
-
μ0H
Pregunta 15
Pregunta
The relative permeability of paramagnetic substance is
Respuesta
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slightly less than 1
-
equal to 1
-
slightly greater than 1
-
very much greater than 1
Pregunta 16
Pregunta
The value of permeability for the free space is
Respuesta
-
4 x 10^-7 Hm-1
-
4π x 10^-7 Hm-1
-
4π x 10^7 Hm-1
-
1/4π x 10^-7 Hm-1
Pregunta 17
Pregunta
The magnetization in any magnetic material appears as a result of
Respuesta
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electrons orbital motion
-
electron spin
-
spin of the nucleus about its axis
-
all of these
Pregunta 18
Pregunta
The sum of the magnetic moments in unit volume of the solid is called
Respuesta
-
field strength
-
magnetism
-
permeability
-
susceptibility
Pregunta 19
Pregunta
Which of the following materials does not have permanent magnetic dipole
Respuesta
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paramagnetic
-
antiferromagnetic
-
diamagnetic
-
ferrimagnetic
Pregunta 20
Pregunta
Interaction between the neighboring dipoles is negligible in case of a
Respuesta
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paramagnetic material
-
diamagnetic material
-
antiferromagnetic material
-
ferrimagnetic material
Pregunta 21
Pregunta
Each ferromagnetic material has characteristic temperature above which its properties are quite different from those below that temperature. That temperature is called
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transition temperature
-
Faraday's temperature
-
demagnetization temperature
-
Curie' temperature
Pregunta 22
Pregunta
The relative permability μ for iron is
Respuesta
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5000
-
7000
-
3000
-
1000
Pregunta 23
Pregunta
Which of the following material is used for making permanent magnets
Respuesta
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carbon steel
-
platinum cobalt
-
Alnico V
-
All of these
Pregunta 24
Pregunta
Which of the following has the highest value of relative permeability
Respuesta
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iron
-
supermalloy
-
Mu-metal
-
4% Si - Fe
Pregunta 25
Pregunta
Ferrimagnetic materials generally behave as a
Respuesta
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semiconductor
-
conductor
-
insulator
-
any of A, B, or C
Pregunta 26
Pregunta
Transformer cores operating at microwave frequency ranges are generally made up of
Respuesta
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ferrites
-
silicon steel
-
supermalloy
-
alnico V
Pregunta 27
Pregunta
The magnetic materials which can be easily magnetized in both directions are known as
Respuesta
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soft magnetic materials
-
hard magnetic materials
-
low hysteresis loss materials
-
high hysteresis loss materials
Pregunta 28
Pregunta
Eddy current loss can be minimized by
Respuesta
-
decreasing the resistance of magnetic medium
-
increasing the resistance of magnetic medium
-
decreasing the permeability of magnetic medium
-
none of these
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