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4

Lenz' law states that the direction of the induced emf and hence current

A. Is determined by the rate of current flux

B. Is found by the right hand rule

C. Is found by the left hand rule

D. Always opposes the cause producing it

Correct Answer :

D. Always opposes the cause producing it


Related Questions

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An effect which is generally used in the gausameter to measure flux density.

A. Skin effect

B. Magnetic effect

C. Hall effect

D. Flywheel effect

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Hysteresis is a phenomenon of _________ in a magnetic circuit.

A. setting up constant flux

B. lagging of H behind B

C. lagging B behind H

D. leading B ahead H

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Hysteresis refers to the ______ between flux density of the material and the magnetizing force applied.

A. Leading effect

B. Ratio

C. Equality

D. Lagging effect

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4

Which of the following is a paramagnetic material?

A. Carbon

B. Copper

C. Bismuth

D. Oxygen

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Theory of ferromagnetic phenomena which assumes each atom is a permanent magnet which can turn freely about its center under the influence of applied field and other magnets.

A. Ewing's theory of ferromagnetism

B. Oersted's ferromagnetism theory

C. Maxwell's magnetic theory

D. Ampere's circuital law

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4

Electric field intensity is a ________.

A. scalar

B. phasor

C. vector

D. variable

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4

The resistance of a material is ____________ its area of cross-section.

A. directly proportional

B. independent of

C. inversely proportional to

D. equal to

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4

Who discovereda the relationship between magnetism and electricity that serves as the foundation for the theory of electromagnetism?

A. Luigi Galvani

B. Hans Christian Oersted

C. Andre Ampere

D. Charles Coulomb

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4

What is the diameter of an atom?

A. About 10^-10 m

B. About 10^-10 cm

C. About 10^-10 mm

D. About 10^-10 �m

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4

A current if flowing east along a power line. If the earth's field is neglecteda the direction of the magnetic field below it is

A. North

B. South

C. East

D. West

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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 evaporation of electrons from a heated surface is called

A. Radiation

B. Convection

C. Thermionic emission

D. Conduction

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4

Used to maintain strength of magnetic field

A. Container

B. Air gap

C. Keeper

D. S ource

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4

The dielectric constant of most materials lies between

A. 1 and 10

B. 10 and 20

C. 20 and 50

D. 50 and 100

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4

The current of electric circuit is analogous to which quantity of a m

A. Mmf

B. Flux

C. Flux density

D. R eluctivity

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4

One coulomb of charge consists of ________ electrons.

A. 624× 10^16

B. 62.4 × 10^16

C. 6.24 × 10^16

D. 0.624 × 10^16

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4

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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Back emf refers to the

A. Current equal to the applied emf

B. Opposing emf

C. Current opposing the applied emf

D. Voltage opposing the applied emf

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4

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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4

When the relative permeability of a material is slightly more than 1a it is called ______ material.

A. diamagnetic

B. ferromagnetic

C. paramagnetic

D. non-magnetic

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4

A good conductor has how many valence electrons?

A.

B.

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If on looking at any one end of a solenoid; the direction of current flow is found to be clockwise then the end under observation is a south pole. This is known as

A. Right hand rule

B. Left hand rule

C. Cork screw rule

D. End Rule

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4

What bond is formed when one or more electrons in the outermost energy orbit of an atom are transferred to another?

A. Ionic

B. Covalent

C. Metallic

D. Van der Waals

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4

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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4

The force acting on a pole of 5 Wb is 25 N. What is the intensity of the magnetic field?

A. 5 N/Wb

B. 25 N/Wb

C. 125 N/Wb

D. 0.2 N/Wb

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4

The phenomenon that when an electric current passes through an anisotropic crystala there is an absorption or liberation of heat due to the non-uniformity in current distribution.

A. Bridgman effect

B. Corona effect

C. Dember effect

D. Destriau effect

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4

The magnetic field around the conductor is determined by the

A. Size of the conductor

B. Amount of current

C. Current divided by the resistance

D. Resistance divided by the current

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4

The electric field intensity between the parallel plate air capacitor is 20 N/C. If an insulating slab of relative permittivity 5 is placed between the platesa then electric field intensity will be

A. 20 N/C

B. 100 N/C

C. 4N/C

D. 40 N/C

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4

A germanium atom has an atomic weight of72. How many neutrons are there?

A.

B.

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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