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ETICC > L Theory 1 > Flashcards

L Theory 1 Flashcards

1
Q

Electrons

A

Electrons are held in orbit to the nucleus by a force of attraction. Negatively charged.

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2
Q

Balanced atom

A

equal amount of protons and electrons

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3
Q

Valence

A

The outer most orbit of the atoms is the valence shell, the electron here is called the valence electron.

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4
Q

Electron flow

A

The electrons will flow from the negative plate to the positive plate.

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5
Q

Conventional current flow

A

This was the belief before that the electrons would flow from positive to negative which is incorrect.

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6
Q

Potential difference

A

PD will exist between any two points in a circuit having a difference in charge i.e. one side has more electrons than the other.

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7
Q

EMF

A

Electromotive force

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8
Q

Voltage production: Chemical

A

negative plate, positive plate. Container, electrolyte and direction of electrons.

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9
Q

Voltage production: friction

A

By rubbing certain materials together you will allow the electrons to move and transfer between them.

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10
Q

Voltage production: induction

A

The key thing is the three prerequisites required to cause magnetic induction – A conductor (wire), a magnetic field and movement.

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11
Q

Voltage production: Pressure

A

Piezo crystals- used in air bag sensors or some lighters

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12
Q

Voltage production: heat

A

Thermocouple

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13
Q

Voltage production: light

A

Semi-conductors

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14
Q

Voltage production: light

A

Semi-conductors

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15
Q

Insulators

A 
Wood
Paper
Rubber
Mica
Insulating varnish
Porcelain
Plastic
Woven fabrics
Glass
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16
Q

Conductors

A 
Copper
Brass
Silver
Carbon
Impure water (salt water)
Aluminium
Platinum
Mercury
Gold
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17
Q

Four factors affecting resistance

A

Type of material, length, cross sectional area and temperature.

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18
Q

Length

A

Longer the cable the more resistance

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19
Q

Cross sectional area

A

Bigger the area, the less resistance

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20
Q

Temperature

A

Increase the temperature you will increase the resistance.

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21
Q

Omhs law

A

current is directly proportional to the applied voltage, as long as the temperature remains constant. Current is inversely proportional to the resistance

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22
Q

Series circuit formula

A

RT= R1+R2+R3

23
Q

Definition of power

A

The rate of doing work

24
Q

Definition of electrical power

A

Number of electrons to be moved and the rate at which they are made to travel

25
Q

How many watts in 1 horsepower

A

746

26
Q

What are fuses used for

A

Protecting the supply

27
Q

What are the two types of fuse used in the RN

A

Cartridge and rupturing capacity fuse

28
Q

How does a fuse work

A

Once a fuse blows it breaks the circuit which means no more current can flow as there is no potential difference. If the gap between the two ends of the fuse is small then sparking can occur so to stop this, quarts powder fills the gap.

29
Q

What is the voltage of earth

A

0 volts

30
Q

The two types of earth return circuits

A

series and parallel

31
Q

What material does magnetism derive from

A

Magnetite

32
Q

What direction does a magnetic field travel

A

North to south

33
Q

What are the lines called in a magnetic field

A

lines of magnetic flux

34
Q

What happens if you connect two same poles together

A

They will repulse eachother

35
Q

What happens if you connect two opposite poles

A

They will attract eachother

36
Q

What are the two types of magnets

A

Horseshoe and bar

37
Q

Temporary magnets

A

Materials that become magnetised then lose their magnetism

38
Q

Materials that produce good magnets

A

Aluminium, nickel and cobalt

39
Q

Magnetic induction

A

a means of creating a magnetic field into a material that is near another magnet

40
Q

What are the two types of current

A

AC(alternating current) DC(direct current)

41
Q

Advantages of AC

A

With AC you can easily change the voltage size using transformers, therefore, it is more adaptable and the equipment is smaller and lighter.

42
Q

Measurement of frequency

A

cycles per second = Hertz

43
Q

Self inductance

A

Because we have now created a moving magnetic field, a voltage is self-induced in the coil which opposes the changing AC current input.

44
Q

What is the unit of inductance

A

The Henry

45
Q

Transformers only work with what current

A

AC

46
Q

What is the voltage called in a transformers secondary coil

A

The EMF of mutual induction

47
Q

What are the two types of transformer

A

Core and shell

48
Q

What is put into a transformer to maximise transfer between primary and secondary coils

A

A soft iron core which enhances the magnetic field

49
Q

Centre tapped transformer

A

Connected to sockets supplying portable equipment to reduce the shock hazard by a half

50
Q

Key components of a single loop generator

A

Wire loop/armature, poles (north and south), slip rings, carbon brushes and the load.

51
Q

What is the most common AC generator

A

Brushless generator

52
Q

Components from a brushless generator

A

HF Generator
AVR (automatic voltage regulator)
Rotating rectifier assembly

53
Q

What does the rotating rectifier assembly do

A

Takes AC from the exciter rotor and converts it to DC

ETICC (11 decks)

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