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The magnetic materials should have a large hysteresis loss for one of the following applications.

A. Transformers

B. ACmotors

C. Permanent Magnets

D. DC generators

Correct Answer :

C. Permanent Magnets


Related Questions

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The force between two magnetic poles is _____ the relative permeability of the medium.

A. directly proportional to

B. independent of

C. inversely proportional to

D. equal to

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A law that states that the current in a thermionic diode varies directly with the three- halves power of anode voltage and inversely with the square of the distance between the electrodesa provided operating conditions are such that the current is limited only by the space charge.

A. Hall's law

B. Joule's law

C. Child's law

D. Coulomb's law

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When a wire loop is rotated in a magnetic field the direction of the induced emf changes one in every _______ revolution

A.

B.

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A magnetic flux of 2.5 x10^4 Wb through an area of 5 x10^4 square meters results in

A. 5 Wb

B. 0.5 Tesia of flux density

C. 5x 10^-5 Wb of flux

D. 5000 Tesia of flux density

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Referred to as the specific reluctance of a material

A. Resistivity

B. Reluctivity

C. Conductivity

D. Permeability

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If the value of 25 of a conductor is 1/230 per oCa then the value of 0is

A. 1/180 peroC

B. 1/150 per oC

C. 1/280 per oC

D. 1/230 per oC

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4

A one cubic cm of copper has how many free electrons at room temperature?

A. 80 × 10^18

B. 8.5 × 10^22

C. 20 × 10^10

D. 50 × 10^20

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One weber of flux is equal to _______ magnetic lines of force.

A. 10^6

B. 10^10

C. 4 × 10^7

D. 10^8

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Which of the following electric quantities is vector in character?

A. Field

B. Charge

C. Energy

D. Potential Difference

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When the relative permeability of a material is much greater than 1a it is called _______ material.

A. diamagnetic

B. ferromagnetic

C. paramagnetic

D. non-magnetic

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A law stating that the magnetic susceptibilities of most paramagnetic substances are inversely proportional to their absolute temperatures.

A. Curie's Law

B. Child's Law

C. CR Law

D. Curie-Weiss Law

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A magnetic pole produces 5000 field lines. How much is the flux in webers? A. 50 × 10^-6

A. 5 × 10^-6

B. 500 × 10^-6

C. 500 × 10^-5

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Refers to the magnetic lines

A. Flux

B. Hysteresis

C. Current

D. Magnetomotive force

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A commercial alloy of aluminum nickela and iron with cobalta copper and titanium added to produce about 12 grades.

A. Alnico

B. Brass

C. Aluminum

D. Constantan

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A magnetic field is

A. The current flow through space around a permanent magnet

B. The force set up when current flows through a conductor

C. The force that drives current through a resistor

D. The force between the plates of a charged capacitor

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Who discovered that a current-carrying conductor would move when placed in a magnetic field?

A. Michael Faraday

B. Andre Ampere

C. Hans Christian Oersted

D. Gustav Robert Kirchhoff

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The direction of force o a current carrying conductor placed in a m found by

A. Cork screw rule

B. Fleming's left hand rule

C. Fleming's right hand rule

D. using a compass

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Which element has four valence electrons?

A. Conductor

B. Insulator

C. Semiconductor

D. Semi- insulator

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The uncharged particles which have no effect on its atomic charge.

A. Nucleons

B. Electrons

C. Protons

D. Neutrons

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What is another name for relative permittivity?

A. Dielectric strength

B. Electric intensity

C. Potential gradient

D. Dielectric constant

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The physical motion resulting from the forces of magnetic fields is called

A. Motor action

B. Rotation

C. Repulsion

D. Torque action

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A law establishing the fact that the algebraic su of the rises and drops of the mmf around a closed loop of a magnetic circuit is equal to zero.

A. Kirchhoff's circuital law

B. Maxwell's circuital law

C. Ampere's circuital law

D. Coulomb's circuital law

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The magnetic flux through a coil changes. This results to the induced emf acting in a direction as to

A. Oppose the change

B. Aid the change

C. Either oppose or aid the change

D. Neither oppose nor aid the change

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Which of the following materials has the least hysteresis loop area?

A. soft iron

B. silicon steel

C. hard steel

D. wrought iron

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The core of a transformer heats up when its primary is fed from an ac source because of

A. permeability

B. ferromagnetism

C. reluctance of core

D. hysteresis loss

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Flux density is measured in

A. Tesia

B. Weber

C. Ampere- turn

D. Maxwell

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A law relating between the magnetic and electric susceptibilities and the absolute temperatures which is followed b ferromagnetsa antiferromagnetsa non-polar ferroelectricsa antiferroelectrics and some paramagnets.

A. Curie's Law

B. Child's Law

C. CR Law

D. Curie-Weiss Law

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When the ferromagnetic substance is inserted in a current- carrying solenoida the magnetic field is

A. Greatly decreased

B. Greatly increased

C. Slightly decreased

D. Slightly increased

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What is the value of the absolute permittivity of air?

A. 8.854 F/m

B. 8.854 × 10^-12 mF/m

C. 8.854× 10^-12 F/m

D. 8.854 × 10^-12 F/m

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The temperature coefficient of resistance of a conductor ______ with an increase in temperature.

A. increases

B. decreases

C. remains the same

D. becomes negative