THEORY OF MACHINE QUIZ

Materials which lack permanent magnetic dipoles are called

dia-magnetic.

None of these

semi-magnetic.

ferro-magnectic.

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Which of the following is the example for piezo-electric material ?

None of these

Lead zirconate titanate

Copper

Potassium niobate

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How many valence electrons would be found in an atom with the atomic number of 51?

8.

5.

51.

none of above.

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Find the odd one out.

Absorptivity.

Emissivity.

Refractive index.

Dielectric strength.

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ALNICO is an alloy of

aluminium, nickel.

aluminium, nickel, iron and cobalt.

iron, cobalt, nickel.

iron, aluminium.

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Maximum number of electrons in a sub-shell with l = 3 and n = 4 is

14.

8.

20.

10.

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Permittivity of free space is equal to

8.854 × 10 - 11 F / m.

8.854 × 10 - 10 F / m.

8.854 × 10 - 12 F / m.

8.854 × 10 - 13 F / m.

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In order to minimise loss due to hysteresis, the magnetic material should have

high resistivity.

low hysteresis coefficient.

large B-H loop area.

high retentivity.

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The core of a transformer for microwave frequency should be made of

silicon.

ferrites.

silicon carbide.

iron.

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In electrical machines the material preferred for pole shoes of electromagnets is

aluminium.

lead.

pure iron.

copper.

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