El Thoery

Question 1

Explain electrical current

Answer 1

The movement of free electrons along a conductor

Question 2

Explain electron flow

Answer 2

Negative to positive , -ve to +ve

Question 3

Explain Conventional current flow

Answer 3

Positive to negative, +ve to -ve

Question 4

Explain ampere

Answer 4

• 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)

Question 5

Circuit symbol for current

Answer 5

I

Question 6

What are the Effects of current flow

Answer 6

Causes heat and sets up a magnetic field around a conductor

Question 7

Potential difference

Answer 7

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

Question 8

What is EMF ?

Answer 8

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

Question 9

Explains voltage

Answer 9

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

Question 10

Voltage production methods

Answer 10

Chemical
Friction
Induction
Pressure
Heat
Light

Question 11

What does Voltage produced through induction - three prerequisites are needed

Answer 11

• an electrical conductor
• A magnetic field
•relative motion

Question 12

What can produced voltage by pressure

Answer 12

Piezo quartz crystal

Question 13

Voltage produced by heat

Answer 13

Thermocouple

Question 14

Voltage produced by light

Answer 14

•artificially manufactured materials
• semiconductors
•solar panels

Question 15

What is a conductor

Answer 15

A material many free electrons, will pass current freely

Question 16

What is a insulator

Answer 16

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

Question 17

What is resistance?

Answer 17

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

Question 18

Insulators

Answer 18

Wood
Paper
Rubber
Mica
Insulating varnish
Porcelain
Plastic
Woven fabrics
Glass

Question 19

Conductors

Answer 19

Copper
Brass
Silver
Carbon
Impure water
Aluminium
Platinum
Mercury
Gold

Question 20

Factors affecting resistance

Answer 20

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

Question 21

Ohms law

Answer 21

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.

Question 22

What is the definition of power

Answer 22

Power is the rate of doing work

Mechanical power formula = force x distance/time

Question 23

Electrical power depends on which two items

Answer 23

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

Question 24

What is 1hp in watts

Answer 24

746w

Question 25

What is electrical unit of power?

Answer 25

Watt (w)

Question 26

What is the mechanical unit of power

Answer 26

Horsepower (hp)

Question 27

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,

Answer 27

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

Question 28

Why is equipment earthed

Answer 28

•safeguards against shocks

Question 29

How does earthing work?

Answer 29

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

Question 30

What is a fuse link ?

Answer 30

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

Question 31

What is a cartridge fuse

Answer 31

A fuse wire in a cylinder of insulating heatproof material

Question 32

What is the disadvantages of a cartridge fuse ?

Answer 32

A voltage could arc even after the fuse has blown.

Question 33

What is a hrc fuse?

Answer 33

High rupturing capacity fuse

Question 34

What insulator is used within a hrc fuse

Answer 34

Quartzs

Question 35

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

Answer 35

Atoms

Question 36

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

Answer 36

Electrons

Question 37

What part of the atom has no charge

Answer 37

Neutron

Question 38

Which part of the atom has a negative charge

Answer 38

Electron

Question 39

Which part of the atom has a positive charge

Answer 39

Proton

Question 40

What is meant by the term “ a balance atom”

Answer 40

Equal amount of electron neutrons and protons

Question 41

In a atom what holds the electrons in orbit of nucleus

Answer 41

Force of attraction

Question 42

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

Answer 42

Free electron

Question 43

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

Answer 43

Valence electron

Question 44

What is the outer shell of an atom know as

Answer 44

Valence she’ll

Question 45

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

Answer 45

Conductor

Question 46

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

Answer 46

Positive charge

Question 47

What is the liquid called that allows electrons

Answer 47

Electrolyte

Question 48

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

Answer 48

From negative to positive

Question 49

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

Answer 49

Positive to negative

Question 50

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

Answer 50

Conventional flow

Question 51

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

Answer 51

Voltage