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Current Affairs January 2024

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4

The temperature coefficient of resistance of semiconductors is

A. positive

B. zero

C. negative

D. infinite

Correct Answer :

C. negative


Related Questions

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4

Permeance of a magnetic circuit is _________ the cross-sectional area of the circuit.

A. directly proportional to

B. inversely proportional to

C. dependent of

D. independent of

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4

When a current carrying conductor is placed in a magnetic fielda the maximum force will act on the conductor when the conductor is at an angle of _______ to the magnetic field.

A. 45o

B. 60o

C. 30o

D. 90o

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4

If the relative permittivity of a material is 10a then its permittivity is

A. 4 × 10^7F/m

B. 4 × 10^-6 F/m

C. 8.854× 10^-11 F/m

D. 8.854 × 10^-12 F/m

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4

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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4

What determines the atomic number of an element?

A. The number of protons

B. The number of electrons

C. The number of neutrons

D. The number of neutrons and protons

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4

The magnitude of the induced emf in a coil is directly proportional to the rate of change of flux linkages. This is known as

A. Joule's Law

B. Faraday's second law of electromagnetic induction

C. Faraday's first law of electromagnetic induction

D. Coulomb's Law

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4

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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4

What is the SI unit of reluctance?

A. At

B. At/m

C. N/Wb

D. At/Wb

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4

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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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

Hipernik is an alloy containing __________ iron and __________ nickel.

A. 40% ; 60%

B. 60% ; 40%

C. 50% ; 50%

D. 70% ; 30%

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4

The net electrical charge in an isolated system remains constant. This is known as

A. Law of conservation of charge

B. Coulomb's first law

C. Coulomb's second law

D. Law of conservation of energy

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4

Which of the following is a diamagnetic material?

A. Aluminum

B. Silver

C. Air

D. Cobalt

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4

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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4

What principle states that each electron in an atom must have a different set of quantum numbers?

A. Inclusion principle

B. Exclusion principle

C. Quantum principle

D. Electron principle

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4

Which of the following magnetic materials can be easily magnetized in both direction?

A. Soft magnetic materials

B. Hard magnetic materials

C. High hysteresis loss materials

D. Low hysteresis loss materials

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4

One of the common application of an air- cored choke.

A. Radio frequency

B. Audio frequency

C. Power supply

D. Power transformer

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4

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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4

Two similar polesa each 1Wba placed 1 m apart in air will experience a repulsive force of

A. 63000 N

B. 63 × 10^-3 N

C. 8 × 10^12 N

D. 796 kN

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4

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

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

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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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

Defined as a closed path in which magnetic induction or flux flows

A. Electric circuit

B. Magnetic circuit

C. Electronic circuit

D. Electromagnetic circuit

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The ratio of the total flux (flux in iron path) to the useful flux (flux in air gap)

A. Leakage flux

B. Leakage current

C. Leakage coefficient

D. Leakage factor

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4

Lenz's law is the consequence of the law of conservation of

A. Energy

B. Charge

C. Field lines

D. Momentum

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4

Magnetic effects of the earth as a huge magnet with north and south poles.

A. Diamagnetic

B. Ferromagnetic

C. Terrestrial magnetism

D. Terrestrial ferromagnetism

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4

If the resistance of a material 2 m long and 2 m^2 in area of cross-section is 1.6 ×10^-8 ?a then its resistivity is

A. 3.2 × 10^-8 ?-m

B. 1.6 × 10^-8 ?-m

C. 0.64 × 10^-8 ?-m

D. 0.16 × 10^-8 ?-m

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4

The lagging effect between flux density of the material and the magne

A. Permeance

B. Eddy current

C. Hysteresis

D. R eluctance

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4

Referred to as the specific reluctance of a material

A. Resistivity

B. Reluctivity

C. Conductivity

D. Permeability