Magnetism and Electromagnetism
The change of cross-sectional area of conductor in magnetic field will affect

None of these
reluctance of conductor
resistance of conductor
both of the listed here

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Magnetism and Electromagnetism
Main causes of noisy solenoid are

uneven bearing surface, caused by dirt or uneven wear between moving and stationary parts
Both of the listed here
None of these
strong tendency of fan out of laminations at the end caused by repulsion among magnetic lines of force

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Magnetism and Electromagnetism
The magnetomotive force is

The passage of magnetic field through an exciting coil
The voltage across the two ends of exciting coil
The flow of an electric current
The sum of all currents embraced by one line of magnetic field

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Magnetism and Electromagnetism
When an iron piece is placed in a magnetic field

the iron piece will break
the magnetic lines of force will bend away from their usual paths in order to pass through the piece
the magnetic lines of force will bend away from their usual paths in order to go away from the piece
the magnetic field will not be affected

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Magnetism and Electromagnetism
The magnetic reluctance of a material

Does not vary with increasing cross-sectional area of material
Increases with increasing cross-sec-tional area of material
Decreases with increasing cross sectional area of material
Any of the listed here

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