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4

Why is it that the magnitude of magnetomotive force required for air gap is much greater than that required for iron part of a magnetic circuit?

A. Because air is a gas

B. Because air has the highest relative permeability

C. Because air is a conductor of magnetic flux

D. Because air has the lowest relative permeability

Correct Answer :

D. Because air has the lowest relative permeability


Related Questions

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How much is the flux in Weber in the above problem?

A. 2 x 10^-5

B. 2 x 10^-3

C. 2 x 10^5

D. 2 x 10^3

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The process by which an emf and hence current is generated or induced in a conductor when there is a change in the magnetic flux linking the conductor is called

A. Electromagnetic induction

B. Mutual induction

C. Faraday's law

D. Electromagnetic interference

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4

The amount of magnetizing force to counter balance the resid magnetic material is referred to as

A. Reluctivity

B. Susceptivity

C. Coercivity

D. Retentivity

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4

A length of wire has a resistance of 10 ohms. What is the resistance of a wire of the same material three times as long and twice the cross-sectional area?

A. 30 ohms

B. 20 ohms

C. 15 ohms

D. 7 ohms

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4

Who developed the electromagnetic theory of light in 1862?

A. Heinrich Rudolf Hertz

B. Wilhelm Rontgen

C. James Clerk Maxwell

D. Andre Ampere

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4

A permanent magnet does not exert a force on

A. an unmagnetized iron bar

B. a magnetized iron bar

C. a moving electric charge

D. a stationary electric charge

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4

The force between two charges placed a given distance apart ______ as the relative permittivity of the medium is increased.

A. increases

B. decreases

C. remains unchanged

D. becomes infinite

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Magnetic field intensity is a ________ quantity.

A. scalar

B. phasor

C. vector

D. variable

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The ability of a mechanically stressed ferromagnetic wire to recognize rapid switching of magnetization when subjected to a dc magnetic field.

A. Wartheim effect

B. Wiedemann effect

C. Wiegand effect

D. Edison effect

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4

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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4

The branch of Engineering which deals with the magnetic effect of electric current is known as

A. Magnetism

B. Electromagnetism

C. Electrical engineering

D. Electronics engineering

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4

If two similar charges 1 coulomb each are placed 1 m apart in aira then the force of repulsion is

A. 8 × 10^6 N

B. 9 × 10 ^9 N

C. 10^6 N

D. 5 × 10^6 N

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4

If a 20 V potential is applied across a relay coil with 50 turns having 1 ? of resistancea the total magnetomotive producing magnetic flux in the circuit is

A. 10 Wb

B. 50 T

C. 1000 A t/m

D. 1000,t

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4

Which of the following has the least number of valence electrons?

A. Conductor

B. Semiconductor

C. Insulator

D. Semi- insulator

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4

The evaporation of electrons from a heated surface is called

A. Radiation

B. Convection

C. Thermionic emission

D. Conduction

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Small voltages generated by a conductor with current in an external magnetic field.

A. Skin effect

B. Magnetic effect

C. Hall effect

D. Flywheel Effect

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4

The temperature coefficient of resistance of insulators is

A. zero

B. negative

C. positive

D. infinite

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Which of the following materials has the highest dielectric strength?

A. Glass

B. Oiled paper

C. Mica

D. Air

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The force which set ups or tends to set up magnetic flux in a magnetic circuit

A. Dynamic force

B. Electromotive force

C. Potential difference

D. Magnetomotive force

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The relation between absolute permittivity of air ( 0)a absolute p and velocity of light (c) is given by

A. 0 0= c^2

B. 0 0= c

C. 1/ 0 0= c

D. 1/ 0 0= c^2

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4

What is the SI unit of reluctance?

A. At

B. At/m

C. N/Wb

D. At/Wb

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Which of the following statements is TRUE?

A. Silicon dioxide is a good

B. The current carriers in conductors are valence electrons

C. For conductorsa the valence electron are strongly attracted to the nucleus

D. The valence electrons are located in the nucleus of an atom

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4

One of the solid structures in which the position of the atoms or ions are predetermined

A. Crystalline solid

B. Amorphous solid

C. Polycrystalline solid

D. Poly amorphous solid

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4

Electric field intensity is measured in

A. volts/meter

B. Newton/meter

C. Newton-meter

D. Amperes/meter

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4

Electric lines of force leave or enter the charge surface at an angle of

A. 30o

B. 45 o

C. 90o

D. depending upon the angle of launch and entry

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4

The magnetic field inside a solenoid

A. is zero

B. is uniform

C. increases with distance from the axis

D. decreases with distance from the axis

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The core of a magnetic equipment uses a magnetic material with

A. Least permeability

B. Low permeability

C. Moderate permeability

D. High permeability

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The conduction of electricity across the surface of a dielectric is called

A. creepage

B. skin effect

C. surface effect

D. crosstalk

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The magnetic potential in a magnetic circuit can be measured in terms of

A. Mmf

B. Emf

C. Farad

D. Coulomb

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Electromotive force in a circuit

A. causes free electrons to flow

B. increases the circuit resistance

C. maintains circuit resistance

D. is needed to make the circuit complete