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175/22/02 > El Thoery > Flashcards

El Thoery Flashcards

1
Q

Explain electrical current

A

The movement of free electrons along a conductor

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2
Q

Explain electron flow

A

Negative to positive , -ve to +ve

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3
Q

Explain Conventional current flow

A

Positive to negative, +ve to -ve

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4
Q

Explain ampere

A

• the unit of measurement of current
•ampere - A
•the amount of electron passing a given point in one second
1 amp= 6.241 x 10 (18)

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5
Q

Circuit symbol for current

A

I

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6
Q

What are the Effects of current flow

A

Causes heat and sets up a magnetic field around a conductor

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7
Q

Potential difference

A

Exits between two points in a circuit having a difference in charge

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8
Q

What is EMF ?

A

Electromotive force - the force that drives the current around a circuit

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9
Q

Explains voltage

A

•Is pressure which causes current flow
•basic unit of measurement of voltage is the volt.
•circuit symbol for voltage is v

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10
Q

Voltage production methods

A

Chemical
Friction
Induction
Pressure
Heat
Light

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11
Q

What does Voltage produced through induction - three prerequisites are needed

A

• an electrical conductor
• A magnetic field
•relative motion

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12
Q

What can produced voltage by pressure

A

Piezo quartz crystal

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13
Q

Voltage produced by heat

A

Thermocouple

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14
Q

Voltage produced by light

A

•artificially manufactured materials
• semiconductors
•solar panels

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15
Q

What is a conductor

A

A material many free electrons, will pass current freely

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16
Q

What is a insulator

A

A material having few free electrons, will only pass current with great difficulty

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17
Q

What is resistance?

A

• opposition to current flow
•basic measurement of resistance is the ohm
•it’s symbol is omega

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18
Q

Insulators

A

Wood
Paper
Rubber
Mica
Insulating varnish
Porcelain
Plastic
Woven fabrics
Glass

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19
Q

Conductors

A

Copper
Brass
Silver
Carbon
Impure water
Aluminium
Platinum
Mercury
Gold

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20
Q

Factors affecting resistance

A

Type of materials - insulator or conductor

Length of conductor - double the length - double resistance…. Half the length -half the resistance.

The cross sectional area can - large csa - low resistance……… small csa - high resistance.

Temperature - hotter/ cooler - resistance higher/lower

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21
Q

Ohms law

A

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 to the resistance.

22
Q

What is the definition of power

A

Power is the rate of doing work

Mechanical power formula = force x distance/time

23
Q

Electrical power depends on which two items

A

• current - the number of electron to be moved
•emf( voltage ) -the rate at which the electrons are made to travel.

24
Q

What is 1hp in watts

A

746w

25
Q

What is electrical unit of power?

A

Watt (w)

26
Q

What is the mechanical unit of power

A

Horsepower (hp)

27
Q

Earth faults are caused by low resistance between the current carrying conductors and earth. This occurs when the insulator resistance of the circuit wiring decreases.

What are the main causes of this,

A

•dampness
•insulation becoming hard or brittle with age or heat
• accidental damage

28
Q

Why is equipment earthed

A

•safeguards against shocks

29
Q

How does earthing work?

A

Current would flow through the earth conductor( ship’s hull) and because it has low resistance this would stole the person getting a shock.

30
Q

What is a fuse link ?

A

Main common type of fuse in the Royal Navy operates the same as a cartridge fuse.

31
Q

What is a cartridge fuse

A

A fuse wire in a cylinder of insulating heatproof material

32
Q

What is the disadvantages of a cartridge fuse ?

A

A voltage could arc even after the fuse has blown.

33
Q

What is a hrc fuse?

A

High rupturing capacity fuse

34
Q

What insulator is used within a hrc fuse

A

Quartzs

35
Q

What are the minute particles called that all matter is mad up of?

A

Atoms

36
Q

In an atom what is the name of the element that revolves around the nucleus

A

Electrons

37
Q

What part of the atom has no charge

A

Neutron

38
Q

Which part of the atom has a negative charge

A

Electron

39
Q

Which part of the atom has a positive charge

A

Proton

40
Q

What is meant by the term “ a balance atom”

A

Equal amount of electron neutrons and protons

41
Q

In a atom what holds the electrons in orbit of nucleus

A

Force of attraction

42
Q

What is an electron know as once is has been forced out of orbit of an atom

A

Free electron

43
Q

What is the name given to the electron furthest away from the the nucleus

A

Valence electron

44
Q

What is the outer shell of an atom know as

A

Valence she’ll

45
Q

In certain material very little energy is need to force electrons out of orbit and enable current flow. What are these material know as

A

Conductor

46
Q

In a basic secondary cel, what charge does the plate have that has lost its electron

A

Positive charge

47
Q

What is the liquid called that allows electrons

A

Electrolyte

48
Q

With reference electron flow what direction do electrons travel in a circuit

A

From negative to positive

49
Q

With reference to conventional current flow what direction do electron travel in a circuit

A

Positive to negative

50
Q

What is the name given to current flow that goes from the positive to negative charge

A

Conventional flow

51
Q

What the name given to the force that drives current around a circuit

A

Voltage

175/22/02 (3 decks)

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