ELECTRICITY AND MAGNETISM FUNDAMENTALS Multiple Choice Questions Part 2

ELECTRICITY AND MAGNETISM FUNDAMENTALS Multiple Choice Questions Part 2


ELECTRICITY AND MAGNETISM FUNDAMENTALS Multiple Choice Questions Part 2

1 Which of the following statements is TRUE?
Silicon dioxide is a good
The current carriers in conductors are valence electrons
For conductors, the valence electron are strongly attracted to the nucleus
The valence electrons are located in the nucleus of an atom

2 How many electrons are needed in the valence orbit to give a material’s stability?
8
4
6
5

3 Residual magnetism refers to the flux density, which exists in the iron core when the magnetic field intensity is
Minimized
Reduced to zero
Maximize
Unity

4 Which of the following is a paramagnetic material?
Carbon
Copper
Bismuth
Oxygen

5 The permeability of permalloy is
Very much greater than permeability of air
Slightly greater than permeability of air
Slightly less than permeability of air
Equal to the permeability of air

6 A t/m is a unit of
Mmf
Emf
Reluctance
Magnetizing force

7 The force between two magnetic poles is  their poles strength.
equal to
directly proportional to
inversely proportional to
directly proportional to the square root of

8 The magnetic energy stored in an inductor is  current.
Directly proportional to
Inversely proportional to
Directly proportional to the square of
Inversely proportional to the square of

9 How is mutual inductance between two coils decreased?
By using a common core
By moving the coils closer
By moving the coils apart
By increasing the number of turns of either coil

10 A magnetic field is
The current flow through space around a permanent magnet
The force set up when current flows through a conductor
The force that drives current through a resistor
The force between the plates of a charged capacitor

11 When the current flows, the magnetic field ……. conductor is in what direction?
The same as the current direction
Opposite the current direction
Omnidirectional
In the direction determined by the left hand rule

12 The magnetic field around the conductor is determined by the
Size of the conductor
Amount of current
Current divided by the resistance
Resistance divided by the current

13 The magnetic flux through a coil changes. This results to the induced emf acting in a
direction as to
Oppose the change
Aid the change
Either oppose or aid the change
Neither oppose nor aid the change

14 A magnetic flux of 2.5 x10^4 Wb through an area of 5 x10^4 square meters results in
5 Wb
0.5 Tesia of flux density
5x 10^-5 Wb of flux
5000 Tesia of flux density

15 Calculate the permeability (in T/A. t/m) of a magnetic material that has a relative
permeability of 300
A.    3.78 x 10^-4
B.    3.78 x 10^-5
C.    3.78 x 10^-3
D.    3.78 x 10^-6

16 Calculate the flux density that will be produced by the field intensity of 2000 a. t/m for a permeability of 126 x 10^-6 T/A.t/m
A.    0.252 G
B.    0.252 x 10^-2 T
C.    0.252 T
D.    0.252 x 10^-2 G

17 How many turns are needed to produce a magnetomotive force of 1000 A.t for a coil with 6 amperes?
6000 turns
600 turns
167 turns
67 turns

18 Amorphous solid is also called
Crystalline
Non- crystalline
Polycrystalline
Homogenous

19 A principle that states that only two electrons with different spins are allowed to exist in a given orbit
Bohr’s principle
Pauli exclusion principle
Avogadro’s principle
Coulomb’s principle

20 What bond is formed when one or more electrons in the outermost energy orbit of an atom are transferred to another?
Ionic
Covalent
Metallic
Van der Waals

21 What bond is formed when electrons in the outermost energy orbits of the atoms are
shared between two or more electrons?
Ionic
Covalent
Metallic
Van der Waals

22 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?
Because air is a gas
Because air has the highest relative permeability
Because air is a conductor of magnetic flux
Because air has the lowest relative permeability

23 Formed when there exist distant electronic interactions between (opposite) charges present in the neighboring atoms or molecules.
Ionic bond
Covalent bond
Metallic bond
Van der Waals bond

24 Defined as the ratio of the volume occupied by the atoms or ions in a unit cell divided by the volume of the unit cell and is used to measure the compactness of a crystal.
Atomic packing factor (APF)
Ionic Packing Ratio (IPR)
Atomic compacting factor (ACF)
Ionic compacting ratio (ICR)

25 What is the maximum number of electrons that can be accommodated in the last orbit of an atom?
4
2
8
18

26 The electrons in the last orbit of an atom are called  electrons.
free
valence
bound
thermionic

27 Which of the following is a paramagnetic material?
Carbon
Bismuth
Copper
Oxygen

28 Whenever a conductor cuts magnetic flux, an emf is induced in it. This is known as
Coulomb’s law
Joule’s law
Faraday’s law
Ohm’s law

29 A law that states that the polarity of the induced voltage will oppose the change in magnetic flux causing the induction.
Joule’s law
Faraday’s law
Coulomb’s law
Lenz’ law

30 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 electrodes, provided operating conditions are such that the current is limited only by the space charge.
Hall’s law
Joule’s law
Child’s law
Coulomb’s law

31 States that the ratio of the thermal conductivity is proportional to the absolute
temperature for all metals.
Wien’s displacement law
Hartleys law
Hall’s law
Wiedemann Franz law

32 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.
Kirchhoff’s circuital law
Maxwell’s circuital law
Ampere’s circuital law
Coulomb’s circuital law

33 The net electrical charge in an isolated system remains constant. This is known as
Law of conservation of charge
Coulomb’s first law
Coulomb’s second law
Law of conservation of energy

34 Lenz’s law is the consequence of the law of conservation of
Energy
Charge
Field lines
Momentum

35 Lenz’ law states that the direction of the induced emf and hence current
Is determined by the rate of current flux
Is found by the right hand rule
Is found by the left hand rule
Always opposes the cause producing it

36 If you hold the conductor with right hand so that the stretched thumb points in the direction of the current, then encircling fingers will give the direction of magnetic lines of force round the conductor. This is known as
Left hand cork screw rule
Right hand cork screw rule
Left hand rule
Right hand rule

37 If the right handed bottle-opener cork screw is assumed to be along the conductor so as to advance in the direction of current flow, the motion of its handle will indicate the direction of magnetic flux produced around the conductor. This is known as
Right hand rule
Left hand rule
Cork screw rule
End rule

38 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
Right hand rule
Left hand rule
Cork screw rule
End Rule

39 If the solenoid is gripped by the right hand with the fingers pointing the direction of current flow, the outstretched thumb will then point the north pole. This is known as
Right hand rule
Helix rule
End rule
Cork screw rule

40 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
Electromagnetic induction
Mutual induction
Faraday’s law
Electromagnetic interference

41 The emf induced in a coil due to the change of its own flux linked with it is called
Mutually induced emf
Dynamically induced emf
Statically induced emf Self induced emf
Self induced emf

42 The emf induced in a coil due to the changing current of another neighboring coil is called
Mutually induced emf
Self induced emf
Statically induced emf
Dynamically induced emf

43 When a conductor is stationary and the magnetic field is moving or changing the emf induced is called
Statically induced emf
Mutually induced emf
Self induced emf
Dynamically induced emf

44 The magnetic potential in a magnetic circuit can be measured in terms of
Mmf
Emf
Farad
Coulomb

45 A substance that attracts pieces iron
Conductor
Semiconductor
Magnet
All of the above

46 The phenomenon by which a subtracts pieces of iron
Magnetism
Electromagnetism
Naturalism
Materialism

47 Which of the following is a natural magnet?
Steel
Magnesia
Lodestone
Soft iron

48 Define as that pole which when placed in air from a similar and equal pole repels it with a
force of newtons
North pole
South pole
Unit pole
Magnetic pole

49 The point in a magnet where the intensity of magnetic lines of force is maximum.
South pole
North pole
Magnetic pole
Unit pole

50 The straight line passing through the two poles of magnet is called
Real axis
Cartesian axis
Magnetic axis
Imaginary axis

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