Electromagnetic Field Theory
Due to which of the following reasons a lightning conductor on top of a building is made into a pointed spike?

Rain drops may not collect
Dust particles may not accumulate
Charge per unit area becomes very high for lightening to discharge
None of these

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Electromagnetic Field Theory
A copper disc is rotated rapidly below a freely suspended magnetic needle. The magnetic needle starts rotating with velocity

 equal to that of disc and in the opposite direction.
 less than that of disc but in opposite direction.
 less than that of disc and in the same direction.
 equal to that of disc and in the same direction.

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Electromagnetic Field Theory
Which of the following statement regarding waveguides is incorrect?

At frequencies below the cut off value the wave progresses across the waveguide after total reflections
Waveguides are usually air filled hollow conducting metallic tubes for transmitting UHF and microwaves
At waveguide can be coupled to a coaxial cable
Waveguides can handle large power at UHF and microwaves

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Electromagnetic Field Theory
Magnetostriction is a phenomenon of

 change in physical dimensions of ferromagnetic materials during magnetism.
 generation of electricity in ferromagnetic materials.
 generation of magnetism in electrical conductors.
 change in permeability of ferromagnetic materials during magnetism.

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