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My Own Study HUB > ELEX 1 COCOON TESTS > Flashcards

ELEX 1 COCOON TESTS Flashcards

1
Q

A type of electricity in which charges are moving.

A

Current

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2
Q

What is considered as the fourth state of matter?

A

Plasma

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3
Q

A particle that retains all the properties of an element is called:

A

Atom

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4
Q

Which of the following is considered as positive charge?

A

Protons and nucleus

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5
Q

The identity of an element can be found commonly on what part of an atom?

A

Nucleus

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6
Q

What is the atomic number of an element with 5 electrons but 4 protons?

A

4

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7
Q

What is the mass of an electron?

A

0.91x10^-30 kg

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8
Q

An atom has a single proton and a single neutron. The element is:

A

Hydrogen

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9
Q

Which of the following shell has the lowest energy level?

A

K

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10
Q

How many electrons reside on the P shell of copper?

A

0

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11
Q

If the number of electrons on the outermost shell of an atom is 3, then 3 is the:

A

Valence

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12
Q

Which of the following valence is the best conductor?

A

2

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13
Q

Which of the following is the best conductor?

A

Silver

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14
Q

When an atom loses an electron it becomes:

A

Both cation and ion

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15
Q

Materials with more free electrons are called:

A

Conductor

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16
Q

A material with a valence of exactly 4 is:

A

Semiconductor

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17
Q

Insulators don’t easily allow electric current to flow because:

A

None of the choices because the answer is that valence electrons of electrons tend to stay on their orbit

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18
Q

It is the band where the outermost electron/s are occupying

A

Valence band

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19
Q

Which of the following electrons are the most energetic?

A

Free electrons

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20
Q

Where do free electrons exist?

A

Conduction band

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21
Q

Which of the following material has the smallest energy gap?

A

Conductor

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22
Q

The band that exist between two allowed band is called:

A

Forbidden band

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23
Q

As the electron orbits closer to the nucleus, it becomes ________.

A

Less energetic

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24
Q

The two forces acting on electrostatics are?

A

Attraction and repulsion

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25
Q

Which is true in electrostatics?

A

None of the choices because electrostatics deals with charges not poles

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26
Q

In the first law of Coulomb’s Law for electrostatics, the force between charges is:

A

Attractive or repulsive

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27
Q

It states that the force between charges is inversely proportional to the square of the distance between them.

A

Second Law of Coulomb’s Law

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28
Q

Permittivity is the ability of a material to _______ the formation of electric field.

A

Resist

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29
Q

Which of the following is unitless?

A

Relative permittivity

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30
Q

It is the field around a charge body.

A

Electric field

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31
Q

Because electric field is invisible, its strength and polarity can be represented with:

A

Electric lines of force

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32
Q

Electric lines of force are polarized from:

A

Positive to negative

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33
Q

An ability of a charged body to attract or repel another charged body expressed in Volts.

A

Electrical potential

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34
Q

The electrical force that attract or repel another charged body expressed in Volts

A

EMF

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35
Q

The difference of potential between two points in an electrical circuit.

A

Potential difference

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36
Q

1 Volt is equivalent to:

A

1J of work to move 1C of charge

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37
Q

A directional movement of charged bodies.

A

Electrical current

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38
Q

1A is equivalent to:

A

1C of charge passing at a point in 1s

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39
Q

Which of the following limits the flow of charge in an electrical circuit?

A

resistance

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40
Q

Which of the following is inversely proportional to Resistance?

A

diameter of the conductor

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41
Q

Which of the following offers a positive temperature coefficient

A

concrete nail

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42
Q

A property of a material to attract iron?

A

Magnetism

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43
Q

The space surrounding a magnet where magnetic forces act.

A

magnetic field

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44
Q

Because magnetic field is invisible, its strength and polarity can be represented with:

A

magnetic lines of force

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45
Q

Magnetic lines of force is polarized from:

A

North to South

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46
Q

Which is true about magnetic poles.

A

None of the choices because magnetic poles does’nt deal with charges instead it deals with poles

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47
Q

The ability of a magnetic material to concentrate magnetic flux.

A

Permeability

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48
Q

Which of the following is the permeability of free space?

A

1.26x10^-6 H/m

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49
Q

Diamagnetic materials has relative permeability:

A

less than 1

50
Q

Materials which act like magnets when subjected to a magnetic field.

A

Paramagnetic

51
Q

Which is true about ferromagnetic materials?

A

u_r&raquo_space;1

52
Q

The force that tends to push out the magnetic flux in a magnetic circuit.

A

Magnetomotive force (MMF)

53
Q

1AT is equal to:

A

1.26 Gilberts (Gb)

54
Q

Magnetic field strength is represented by:

A

H

55
Q

Oersted is equivalent to:

A

Gb/cm (Gilberts per centimeter)

56
Q

1Wb is equal to:

A

1x10^8 lines

57
Q

The number of magnetic lines of force per unit area of a section perpendicular to the direction of flux.

A

Magnetic flux density (B)

58
Q

Which of the following is a unit of Flux density?

A

Tesla (T)

59
Q

What is the Law for Electromagnetic Induction?

A

Faraday’s Law

60
Q

States that when a conductor cuts a magnetic flux, the conductor induces its own EMF

A

1st Law of Faraday

61
Q

Electromagnets are types of magnets made by:

A

conductor coil with current

62
Q

The totality of magnetic lines of force going out from a magnet.

A

Magnetic Flux

63
Q

The amount of induced EMF in a coil cutting a magnetic flux is directly proportional to the rate at which the flux is being cut. This is described by:

A

2nd Law of Faraday

64
Q

The induced EMF is directly proportional to:

A

number of coil turns

65
Q

Flux rate can be expressed as:

A

both Wb/s and Mx/s

66
Q

The law that determines the polarity of the induced voltage.

A

Lenz’s Law

67
Q

In the left hand rule for coils, the thumb points to:

A

The direction of north pole

68
Q

In the left hand rule for current carrying conductors, the thumb points to:

A

the direction of current

69
Q

In the left hand rule for generators, the thumb points to:

A

the direction of cutting

70
Q

Lenz’s law states that, the magnetic field of the induced current must oppose the:

A

magnetic field of the flux being cut

71
Q

If a neutral atom loses one of its valence electrons, it becomes a(n)

A

Both Electrically charged atom and Positive ion

72
Q

Aluminum, with an atomic number of 13, has

A

Both 3 valence electrons and 13 protons in its nucleus

73
Q

The atomic number of an element is determined by:

A

The number of protons.

74
Q

In a compound:

A

There must always be two or more elements.

75
Q

In a metal conductor, such as a copper wire,

A

Free electrons are the moving charges that provide current

76
Q

Of the following substances, the worst conductor is:

A

Air

77
Q

If a material has low resistance:

A

It is a good conductor.

78
Q

Which of the following statements is true?

A

Both Like charge repel each other and Unlike charge attract each other

79
Q

Which of the following statements is true?

A

Voltage can exist without current

80
Q

One ampere of current corresponds to

A

1C/1s

81
Q

What is the output voltage of a battery expends 12J of energy in moving 1.5C of charge?

A

8V

82
Q

The current which flows when 0.1 coulomb is transferred in 10ms is:

A

10A

83
Q

A stroke of lightning:

A

Is a discharge of static electricity

84
Q

In some batteries, chemical energy can be replenished by:

A

Charging it

85
Q

A positive electric pole:

A

Has a fewer electrons than the negative pole.

86
Q

The total flux in the core of an electrical machine is 20mWb and its flux density is 1T, The cross-sectional area of the core is:

A

0.02m^2

87
Q

A coil of 100 turns is wound uniformly on a wooden ring. The ring has a mean circumference of 1m and a uniform cross-sectional area of 10 cm^2. The current in the coil is 1A. The magnetic field strength is:

A

100 A/m

88
Q

Which of the following statements is false?

A

The remanence of a ferrous material is measured in ampere/meter

89
Q

Two bar magnets are placed parallelto each other and about 2 cm apart, suct that the south pole of one magnet is adjacent to the north pole of the other. With this arrangement, the magnets will:

A

Attract each other

90
Q

The tesla (T) is a unit of

A

flux density

91
Q

A commercial permanent magnet will last indefinitely if it is not subjected to

A

a strong demagnetizing field, physical shock, and high temperatures

92
Q

If the north (N) pole of a permanent magnet is placed near a piece of soft iron, what is the polarity of the nearest induced pole?

A

South (S) pole

93
Q

A material that becomes strongly magnetized in the same direction as the magnetizing field is classified as

A

ferromagnetic

94
Q

1 uWb (MicroWeber) equals

A

100 Mx (Maxwells)

95
Q

When a small voltage is generated across the width of a conductor carrying current in an external magnetic field, the effect is called

A

The HALL Effect

96
Q

With an electromagnet,

A

Both more current and more coil turns mean a stronger magnetic field and if there is no current in the coil, there is no magnetic field

97
Q

When a magnetic flux of 10Wb links with a circuit of 20 turns in 2s, the induced e.m.f. is:

A

100V

98
Q

A conductor carries a current of 10A at right-angles to a magnetic field having a flux density of 500 mT. If the length of the conductor in the field is 20cm, the force on the conductor is:

A

1N

99
Q

An electric bell depends for its action on:

A

an electromagnet

100
Q

The magnetic field due to a current-carrying conductor takes the form of:

A

concentric circles

101
Q

Which of these can represent magnetomotive force?

A

The ampere-turn.

102
Q

A coil has 500 turns and carries 75 mA of current. The magnetomotive force will be:

A

37.5 At

103
Q

The change in the direction of a compass needle, when a current-carrying wire is brought near, is:

A

Electromagnetic deflection

104
Q

Geomagnetic lines of flux:

A

Are horizontal at the geomagnetic equator

105
Q

The force between a magnet and a piece of ferromagnetic metal that has not been magnetized:

A

Is never repulsive.

106
Q

A unit of overall magnetic field quantity is the:

A

Maxwell

107
Q

An advantage of an electromagnet over a permanent magnet is that:

A

An electromagnet can be switched on and off.

108
Q

A relay is connected into a circuit so that a device gets a signal only when the relay coil carries a current. The relay is probably:

A

Normally open

109
Q

A high tape-rcorder motor speed is generally used for:

A

Video

110
Q

An advantage of a magnetic disk, as compared with magnetic tape, for data storage and retrieval is that:

A

Data can be stored and retreived more quickly with disks than with tapes.

111
Q

For the current-carrying conductor lying in the magnetic field shown in figure (a) below, the direction of the force on the conductor is: (use conventional current flow and dot means current is towards you)

A

upwards

112
Q

For the current-carrying conductor lying in the magnetic field shown in figure (b), the direction of the cureent in the conductor is: :(use conventional current flow and dot means current is towards you)

A

towards the viewer

113
Q

Suppose a certain current in a galvanometer causes the needle to deflect 20 degrees, and then this current is doubled. The needle deflection:

A

will increase

114
Q

Lines of magnetic flux are said to originate:

A

At a north magnetic pole

115
Q

If a conductor is horizontal, the current flowing from left to right and the direction of the surrounding magnetic field is from above to below, the force exerted on the conductor is: :(use conventional current flow)

A

away from the viewer

116
Q

A bar magnet is moved at a steady speed of 1.0 m/s towards a coil of wire which is connected to a center-zero galvanometer. The magnet is now withdrawn along the same path at 0.5 m/s. The deflection of the galvanometer is in the:

A

opposite direction as previously, with the magnitude of the deflection halved.

117
Q

The point at which a magnetic material loses its ferrromagnetic properties is called the

A

Curie temperature

118
Q

The flux density in the iron-core of an electromagnet is 0.25 T. When the iron-core is removed, the flux density drops to 62.5 x 10^-6 T. What is the relative permeability of the iron core?

A

ur= 4000

119
Q

The flux density in the iron-core of an electromagnet is 0.25 T. When the iron-core is removed, the flux density drops to 62.5 x 10^-6 T. What is the relative permeability of the iron core?

A

ur = 4000

120
Q

The force on an electron travelling at 10^7 m/s in a magnetic field of density 10uT is 1.6 x 10^-17N. The electron has a charge of:

A

1.6 x 10^-19C

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