L Theory 1

Question 1

Electrons

Answer 1

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

Question 2

Balanced atom

Answer 2

equal amount of protons and electrons

Question 3

Valence

Answer 3

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

Question 4

Electron flow

Answer 4

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

Question 5

Conventional current flow

Answer 5

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

Question 6

Potential difference

Answer 6

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.

Question 7

EMF

Answer 7

Electromotive force

Question 8

Voltage production: Chemical

Answer 8

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

Question 9

Voltage production: friction

Answer 9

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

Question 10

Voltage production: induction

Answer 10

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

Question 11

Voltage production: Pressure

Answer 11

Piezo crystals- used in air bag sensors or some lighters

Question 12

Voltage production: heat

Answer 12

Thermocouple

Question 13

Voltage production: light

Answer 13

Semi-conductors

Question 14

Voltage production: light

Answer 14

Semi-conductors

Question 15

Insulators

Answer 15

Wood
Paper
Rubber
Mica
Insulating varnish
Porcelain
Plastic
Woven fabrics
Glass

Question 16

Conductors

Answer 16

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

Question 17

Four factors affecting resistance

Answer 17

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

Question 18

Length

Answer 18

Longer the cable the more resistance

Question 19

Cross sectional area

Answer 19

Bigger the area, the less resistance

Question 20

Temperature

Answer 20

Increase the temperature you will increase the resistance.

Question 21

Omhs law

Answer 21

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

Question 22

Series circuit formula

Answer 22

RT= R1+R2+R3

Question 23

Definition of power

Answer 23

The rate of doing work

Question 24

Definition of electrical power

Answer 24

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

Question 25

How many watts in 1 horsepower

Answer 25

746

Question 26

What are fuses used for

Answer 26

Protecting the supply

Question 27

What are the two types of fuse used in the RN

Answer 27

Cartridge and rupturing capacity fuse

Question 28

How does a fuse work

Answer 28

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.

Question 29

What is the voltage of earth

Answer 29

0 volts

Question 30

The two types of earth return circuits

Answer 30

series and parallel

Question 31

What material does magnetism derive from

Answer 31

Magnetite

Question 32

What direction does a magnetic field travel

Answer 32

North to south

Question 33

What are the lines called in a magnetic field

Answer 33

lines of magnetic flux

Question 34

What happens if you connect two same poles together

Answer 34

They will repulse eachother

Question 35

What happens if you connect two opposite poles

Answer 35

They will attract eachother

Question 36

What are the two types of magnets

Answer 36

Horseshoe and bar

Question 37

Temporary magnets

Answer 37

Materials that become magnetised then lose their magnetism

Question 38

Materials that produce good magnets

Answer 38

Aluminium, nickel and cobalt

Question 39

Magnetic induction

Answer 39

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

Question 40

What are the two types of current

Answer 40

AC(alternating current) DC(direct current)

Question 41

Advantages of AC

Answer 41

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

Question 42

Measurement of frequency

Answer 42

cycles per second = Hertz

Question 43

Self inductance

Answer 43

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

Question 44

What is the unit of inductance

Answer 44

The Henry

Question 45

Transformers only work with what current

Answer 45

AC

Question 46

What is the voltage called in a transformers secondary coil

Answer 46

The EMF of mutual induction

Question 47

What are the two types of transformer

Answer 47

Core and shell

Question 48

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

Answer 48

A soft iron core which enhances the magnetic field

Question 49

Centre tapped transformer

Answer 49

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

Question 50

Key components of a single loop generator

Answer 50

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

Question 51

What is the most common AC generator

Answer 51

Brushless generator

Question 52

Components from a brushless generator

Answer 52

HF Generator AVR (automatic voltage regulator) Rotating rectifier assembly

Question 53

What does the rotating rectifier assembly do

Answer 53

Takes AC from the exciter rotor and converts it to DC