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Current Affairs January 2024

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4

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

Correct Answer :

C. Child's law


Related Questions

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Formed when there exist distant electronic interactions between (opposite) charges present in the neighboring atoms or molecules.

A. Ionic bond

B. Covalent bond

C. Metallic bond

D. Van der Waals bond

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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

Who demonstrated that there are magnetic effects around every current-carrying conductor and that current-carrying conductors can attract and repel each other just like magnets?

A. Luigi Galvani

B. Hans Christian Oersted

C. Charles Coulomb

D. Andre Ampere

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The magnetic flux of 2000 lines is how many Maxwells?

A.

B.

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The induced emf in a wire loop that is moved parallel to a uniform magnetic field is

A. Zero

B. Dependent on the area of the loop

C. Dependent on the shape of the loop

D. Dependent on the magnitude of the field

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The magnetic field of a magnetized iron bar when strongly heated

A. Becomes weaker

B. Becomes stronger

C. Reverses in direction

D. is unchanged

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4

The potential at a point due to a charge is 15 V. If the distance is times, the potential at the point will be

A. 5 V

B. 18 V

C. 45 V

D. 15 V

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A 200-watt lamp working for 24 hours will consume approximately _____ units.

A.

B.

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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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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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Refers to the magnetic lines

A. Flux

B. Hysteresis

C. Current

D. Magnetomotive force

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The B-H curve of ________ is not a straight line.

A. air

B. wood

C. silicon steel

D. soft iron

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4

The temperature coefficient of resistance of semiconductors is

A. positive

B. zero

C. negative

D. infinite

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The resistivity of a conductor ___________ with an increase in temperature.

A. increases

B. decreases

C. remains the same

D. becomes zero

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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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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

If the value of 25 a conductor is 1/255 per oCa then the value of 20is

A. 1/300 per oC

B. 1/250 peroC

C. 1/230 per oC

D. 1/260 per oC

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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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If the distance between two magnetic poles decreases by 2 timesa the force between them

A. decreases two times

B. increases four times

C. increases two times

D. decreases four times

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4

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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What is the SI unit of specific resistance or resistivity?

A. Ohm-circular mil per inch

B. Ohm-circular mil per foot

C. Ohm-m

D. Ohm-cm

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When the current flowsa the magnetic field ��. conductor is in what direction?

A. The same as the current direction

B. Opposite the current direction

C. Omnidirectional

D. In the direction determined by the left hand rule

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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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Materials whose permeabilities are slightly greater than that of free space

A. Paramagnetic

B. Non- magnetic

C. Ferromagnetic

D. Diamagnetic

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What revolves about the positive nucleus in a definite orbit?

A. Atom

B. Proton

C. Electron

D. Neutron

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Hysteresis loss can be reduced by one of the following.

A. Increasing mmf of the circuit

B. Using material narrow hysteresis loop

C. Using ferromagnetic core

D. Laminating the magnetic circuit

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The energy stored in an electrostatic field or electromagnetic field is called

A. Electromagnetic energy

B. Kinetic energy

C. Potential energy

D. R est energy

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Refers to the non- metallic materials that have the ferromagnetic properties of iron.

A. Ferrites

B. Ferromagnetic

C. Diamagnetic

D. Paramagnetic

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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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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