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L theory > L Theory > Flashcards

L Theory Flashcards

1
Q

What is contained in the nucleus of an atom?

A
  1. Positively charged protons

2. Neutral Neutrons

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2
Q

What holds Electrons in orbit around around the nucleus?

A

A. The force of attraction

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3
Q

Is an electron charged positively or negatively?

A

Negatively

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4
Q

Name the outer most shell of an atom.

A

Valence shell.

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5
Q

What is the outer most electron called?

A

Valence electron.

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6
Q

How do electrons move along a conductor?

A

Negative to positive.

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7
Q

What is conventional current flow?

A

Positive to negative

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8
Q

What is the unit of measurement for current?

A

Amps

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9
Q

What atom is this?

A

Hydrogen.

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10
Q

Define current.

A

The amount of electrons passing a given point in one second.

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11
Q

What is another word for voltage?

A

A. EMF (Electromotive force)

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12
Q

Define Electromotive force.

A

A. Electromotive force is what drives the current around the circuit.

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13
Q

What is the measurement of voltage?

A

Volts

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14
Q

State the 6 methods by which voltage can be produced.

A
  1. Chemical
  2. Friction
  3. Induction
  4. Pressure
  5. Heat
  6. Light
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15
Q

How is voltage created by friction?

A

A. By rubbing 2 different materials together.

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16
Q

Which 3 prerequisites must be met to create voltage by induction?

A
  1. An electrical conductor
  2. A magnetic field
  3. Relative movement
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17
Q

Which crystal is used in crash sensors for airbag systems?

A

Piezo quartz

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18
Q

What symbol is used for Current?

A

I

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19
Q

What factors affect the amount of voltage produced in a thermocouple?

A
  1. The 2 materials used for the wires

2. The temperature differential

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20
Q

What is another word for solar panel? And what does this component do?

A
  1. Semiconductor

2. Generates voltage when exposed to light by changing it’s electrical charge.

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21
Q

Name this symbol and what it represents in a circuit.

A
  1. Omega

2. Resistance

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22
Q

What is resistance?

A

Opposition to current flow

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23
Q

Name 4 insulators.

A
  1. Wood
  2. Paper
  3. Rubber
  4. Mica
  5. Insulating varnish
  6. Porcelain
  7. Plastic
  8. Woven fabrics
  9. Glass
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24
Q

Name 4 conductors.

A
  1. Copper
  2. Brass
  3. Silver
  4. Carbon
  5. Impure water (salt water)
  6. Aluminium
  7. Platinum
  8. Mercury
  9. Gold
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25
Q

State the 4 factors that affect the resistance of a conductor.

A
  1. Type of material
  2. Length of conductor
  3. Cross sectional area
  4. Temperature
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25
Q

State the 4 factors that affect the resistance of a conductor.

A
  1. Type of material
  2. Length of conductor
  3. cross sectional area
  4. Temperature
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26
Q

State Ohm’s law.

A

A. Ohm’s law states that a current flowing through a conductor is directly proportional to the applied voltage across it, providing the temperature remains constant, and is inversely proportional to the resistance.

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27
Q

Define power.

A

Power is the rate of doing work.

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28
Q

What is the equation for calculating mechanical power?

A

Power = Force x distance / time

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29
Q

What does electrical power depend on?

A
  1. The number of electrons to be moved

2. The rate at which they are made to travel

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30
Q

What is the equation for calculating electrical power?

A

A. Power = current x voltage (p = I x V)

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31
Q

State the unit of measurement for electrical power.

A

A. Watt

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32
Q

State the mechanical unit of power.

A

Horsepower

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33
Q

How many watts is equivalent to 1 horsepower?

A

A. 746 Watts

34
Q

Resistors are rated using which measurements?

A
  1. Watts 2. Ohms
35
Q

What is the purpose of a fuse?

A

A. To protect the power source.

36
Q

Name this fuse and state why the RN uses a glass casing rather than porcelain.

A

Cartridge fuse. the glass casing allows inspection of the wire.

37
Q

Name the other fuse used within the RN and state the break down process.

A

A. High rupturing capacity fuse (HRC) Once the silver fusing element melts, the quartz powder will heat up and liquify flowing between the broken ends of the fusing element. The electricity cannot arc in this setup due to the fact that quartz is an insulator.

38
Q

What is the potential difference of the earth? (and sea)

A

A. Zero volts

39
Q

Name the 3 factors that cause earth faults.

A
  1. Dampness
  2. Insulation becoming hard or brittle with age or heat.
  3. Accidental damage
40
Q

What happens when 2 similar poles are brought together? ( north and north or south and south)

A

There is a force of repulsion between them due to their respective magnetic fields.

41
Q

What are the magnets used within the RN?

A
  1. Bar

2. Horseshoe

42
Q

Name the elements added to steel alloys to produce a stronger magnet.

A
  1. Aluminium
  2. Cobalt
  3. Nickel
43
Q

What are the 2 advantages of AC over DC?

A
  1. Wiring and equipment can be lighter

2. Transformers can be used in conjunction.

44
Q

What makes up one cycle of a sine wave?

A
  1. positive half cycle

2. Negative half cycle

45
Q

Define frequency. Name the unit of measurement for frequency.

A
  1. Number of cycles completed in one second

2. Hertz

46
Q

How can a piece of wire become a basic inductor?

A

By being shaped into a coil.

47
Q

what is the unit of measurement for inductance?

A

Henry (H)

48
Q

Name the EMF generated in the second coil of the transformer.

A

EMF of mutual induction

49
Q

What are the 2 types of transformers?

A
  1. Core type transformer

2. Shell type transformer

50
Q

How is maximum transfer achieved between primary and secondary windings?

A

The windings are wound onto a laminated soft iron core.

51
Q

Why are windings wound onto a laminated soft iron core?

A

To achieve maximum transfer between primary and secondary windings.

52
Q

Why do we fit centre tapped transformers to supply sockets?

A

To reduce the shock effect by half from 115 v to 57.5 v

53
Q

What is the colour coding for input cables on HM ships

A

Red - L1
yellow - L2
Blue - L3

54
Q

What is the colour coding for output cables on HM ships?

A

Red - A
yellow -B
Blue C

55
Q

What are the new colour codes for input cables?

A

Brown - L1
Black - L2
Grey - L3

56
Q

What are the new colour codes for output cables?

A

Brown - A Black - B Grey - C

57
Q

What are the 2 types of generator used in the RN?

A
  1. Single loop generator

2. Brushless generator

58
Q

What is the most common generator in the RN?

A

Brushless generator

59
Q

What is the purpose of a high frequency generator?

A

The HF generator supplies voltage to the windings of the AC exciter via the automatic voltage regulator. (AVR)

60
Q

What is the purpose of an automatic voltage regulator?

A

The AVR supplies a DC to the AC exciter and maintains the generator output voltage at 450 volts.

61
Q

What is the purpose of the rectifier assembly?

A

It converts the AC exciter output to DC.

62
Q

What is an electric motor?

A

An electric motor is a machine for converting electrical energy into mechanical energy.

63
Q

What are the 2 main reasons for using AC motors?

A
  1. AC motors require less maintenance

2. AC motors are more efficient than a DC motor of the same size.

64
Q

State the two main components of an AC induction motor.

A
  1. rotor 2. stator
65
Q

What is the main disadvantage of the AC induction motor?

A

It is very difficult to vary speed without without specialist equipment.

66
Q

What parts of the stator would need to be labelled in an exam.

A
  1. Stator slots
  2. Space for ventilation
  3. outer casing
  4. Stator core
67
Q

What is the most common type of rotor used in HM ships?

A

Squirrel cage.

68
Q

What parts of the rotor need to be labelled in an exam?

A
  1. Copper bars
  2. Shaft
  3. non-drive end bearing
  4. drive end bearing
    5 copper end ring at both ends of the rotor.
69
Q

What causes the rotor to rotate?

A

The rotating magnetic field of the stator induces a current in the copper bars of the rotor, this current causes a magnetic field to be set up around the rotor. This magnetic field is opposite in polarity to the magnetic field in the stator. The interaction between this field and the rotating field of the stator causes the rotor to follow the rotating field therefore giving you rotation.

70
Q

What are the 2 ways of connecting a 3 way motor?

A
  1. Star

2. Delta

71
Q

What needs to be labelled on a diagram of Maxwell’s corkscrew rule

A
  1. Direction of electric current
  2. Magnetic field and direction of travel
  3. Right hand
  4. Electric conductor
72
Q

What needs to be labelled in a diagram of Fleming’s left hand rule?

A
  1. The left hand
  2. Thumb = Motion of conductor
  3. First finger = Field
  4. Second finger = current
73
Q

What causes Back EMF?

A

The movement of the loop in an DC motor causes it to cut the magnetic field of the magnet and causes an EMF to be induced into the conductor.

74
Q

How is torque produced?

A

By the turning force of a motor.

75
Q

The amount of torque produced by an electric motor is dependent upon 2 things, what are they?

A
  1. Strength of the magnetic field

2. Magnitude of the armature current.

76
Q

What are the 3 classifications of DC motor?

A
  1. Series
  2. Shunt
  3. Compound
77
Q

What is a compound motor?

A

It is a combination of series and shunt motors.

78
Q

What are the 2 neutral axis’ associated with DC motors?

A
  1. Magnetic neutral axis

2. Geometric neutral axis

79
Q

What is an armature reaction?

A

It is where the armature magnetic field will distort the field winding magnetic field.

80
Q

State the purpose of interpoles.

A

Interpoles assist in giving sparkless commutation by neutralising the effect of armature reaction.

81
Q

What direction do the lines of magnetic flux travel?

A

They leave the magnet at the north pole and re-enter at the south.

82
Q

The level to which the voltage or current rises to is called?

A

Amplitude

83
Q

What are the values of the ships main electrical supplies?

A

3 phase, 60 hertz, 450 volts

L theory (1 decks)

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