M3 Flashcards
Are protons negatively charged
No, they are positively charged
What is a neutron
Neutral particles with a charge of 0. They ensure that positively charged protons don’t repel.
What is an electron
A negatively charged particle that travels on the shells or orbits.
Why don’t electrons move away from the nucleus
Because of the centrifugal force which attracts the electrons towards the positively charged protons.
When is an atom electrically neautral
When number of protons and electrons is the same
What is an ion
A positive or negatively charged atom. Happens through ionisation
What is a molecule
An electrically neutral group of two or more atoms held together by chemical bonds. Distinguished by their lack of electrical charge.
What is a cation
A positively charged ion
What is an anion
A negatively charged ion
What do cations and anions do together
They attract to each other and form ionic compounds like salts
what is a compound
A chemically bonded substance so posed of two or more identical molecules. Composed of atoms from more than one element.
What are the four types of bonds
Convalent bonds
Ionic bonds
Inter metallic compounds
Certain complexes held together by coordinate covalent bonds
What is a conductor
It has less than 4 electrons. 3 or less in valance shell.
What are the characteristics of a conductor
Metals
Closely packed and have a crystal lattice
High density, which allows electrons on outer shell to separate from their atoms and move within the atomic structure.
Hugh mobility of electrons
What is a semiconductor
An atom that has 4 electrons
Conductivity is produced by adding other forge in atoms - dopping
What are some example of semi conductors
Silicon
Germanium
What is an insulator
Also known as non conductors
Has more than 4 electrons on valence shell.
Has no free electrons therefore cannot be conducted
The structure of electrons is tightly packed therefore means electrons cannot break away
What is an example of insulators
Micra
Porcelain
What is static electricity
When two materials are rubbed against each other and some electrons from one material are handed over to the other material. The electrons that are given are called free electrons and are in the valence shell
How can static electricity be produced
Contact
Friction
Induction
What is an example of static friction
When a glass rod is rubbed with fur it becomes negatively charged. Whereas if it is rubbed with silk it becomes positively charged
What is the law of attraction
Opposites attract
What happens to the lines of force
They extend in all directions from the charged body and terminate where there is an opposite charge
Why are metals good conductors
As they have a vast number of free electrons available
What happens when you apply a force to a solid
Electrons flow from a negative to the positive pole
What happens when an electron enters a conductor
Another electron at opposite end of conductor is pushed out.
What is the movement of an electron called
Current
What happens if the current remains constant
The same number of electrons flow through a conductor regardless of its cross section area
What does it mean if a conductors cross section is smaller
It means the electrons are more closely packed together. Therefore heating is higher. Therefore electron ion collisions occur more often with higher intensity. Increasing heating.
What is the formula for current density
Current density = Current [A] / cross section area [mm2]
J = I / A
What does a greater density in a conductor mean
More heat is produced.
What is the maximum a cable can be heated to
60 degree c. For each given cross section an ambient temp of 25 degrees c
Is water a conductor
Pure water is not a conductor. As it does not contain any ions so electrons do not move through the solution
Is Tap water a conductor $$$$$$
Yes. As it contains hydrogen and oxygen. Of DC is applied hydrogen is generated at negative pole and oxygen at positive.
What is it meant by the decomposition of chemical compounds
The passing of an electric current through a liquid which is called electrolysis. The conducting substance is called an electrolyte
What is an electrolyte
The conducting substance that occurs when an electric current passes through
Where can you find the condition of electricity in gases
The application of gases can be found in the filament builds with a higher electrical output of 60w
Why would you find a gas in a filament light bulb
To prevent it from burning oxidising or vaporising. Gases such as nitrogen argon and krypton
What is the production of electrical continuity in gasses or metal vapours
The production of light
What is the process of light by gasses called
It is called gas discharge, happens to fluorescent tubes
Why does gas discharge happen
Due to the heat. The molecules or atoms move to and from random layers without combining with each other. The gas atoms that are enclosed in the bulbs are electrically neutrals so no need to combine.
Electrons of fewer atoms will split if for energy supply then freely moving charge carriers are generated. The current increases in such a way that it has to be limited with resistance.
What does gas discharge arise from
Electrons and positive ions therefore being it neutral.
What is an oscilloscope
Provides a visual isotion of rapidly varying processes in electrical engineering
What is an oscillograph
Rapidly varying electrical process which can be permanently recorded. Whereas using a oscilloscope the processes can be visualised but not recorded. More so pictures.
Do more on oscilloscope etc
What is potential difference
Always arises between two differently charged points. When there is an deficiency of electrons at one point and an excess at another point.
How do you generate voltage
By separating negative and positive charges
What is a generator
It draws electrons from positive pole and transports them to negative pole so potential difference is maintained and therefore produces an electrical voltage. Not the only way to produce it tho.
Add more on how to produce voltage.
What is EMF
electromotive force.
What does the electromotive force do.
A force that acts in a way that a body is pushed pulled or lifted. As electrical charges will exert a push or pull force on each other without actually coming into contact with each other.
Who developed the electric field theory
Faraday
How can electrical attraction and repulsion was shown
By electrical flux line. Yet they are invisible in real life. The more lines the stronger the field would be. The lines also take the shortest means possible to get from a positive to a negative charge.
What does the density of flux lines red present
The quantity of electrical excitement between charges
What is voltage
Also known as electric pressure. It’s the difference in electrical potential between two points. The force that acts on electron to cause it to move.
What does distance between for an electron and nucleus
The greater distance between the electron and nucleus the stronger the potential energy of electron.
What is DC
Direct current. The charge carriers consistently flow in same direction at same current
What is AC
Alternative current. A flow of charges repeatedly changing direction and current in a certain time period
What is the value of 1 ampere
6.24 x10 18 electron/sec
How can you measure current
Ammeter or current meter
What is the charge of a single electron
-0.1602 x 10 -18 C
How many electrons are in the valance shell for a good conductor
3 or less
If you were to rub a glass rod with silk it would become what charge
Positive
Opposite charges do what and like charges do what
Opposite charge and like charges repel
What is a battery made up off
Two different materials and an electrolyte
If you increase distance between electron and neutron what happens
Potential energy/ voltage increases
What will a nickel cadmium cells voltage be when it is discharged
1 volt
What would chromel alumels mv change by its temperature increases by 100 degrees c
353.5volts
What is superimposed voltage
Goes below zero but inconsistent to rest of graph
What is a generator
A device which separates charge
What is emf
Electromotive force
How does current density affect heat
The greater the current density the more heat that’s produced
What is the liquid in electrolysis
Electrolyte
What is gas discharge
The electrical continuity in gases or metal vapour which results in light
What is the speed of movement of charges depends on
Temp
Cross section
Conductor materials
What is 1 amp
6.24 x 10(18)
What’s the device called for recording oscillations?
Oscilloscope
What are the two kinds of voltage and what do they do
AC - changes polarity
DC - same polarity (direction)
Is pure water a conductor?
No but tap water is as it has other chemicals in it
What is the maximum temperature for cables
60 degrees
What is testing temp for cables
25 degrees Celsius
How to work out current density
Current/ cross sectional area
What charge does a glass rod have when rubbed with fur and silk
Fur - negative
Silk - positive
Examples of insulators
Porcelain
What is doping
Adding foreign atoms
Insulators have how many electrons in valance orbit
5 or more
Semi conductors have how many electrons in valance orbit
Exactly 4
Good conductors have fun how many electrons in valence orbit?
3 or less
Four types of bonds
Covalent, ionic, intermetallic, coordinate covalent
What happens to conductance when resistance is high
Low conductance
Charge of an electron
-0.1602 x 10 (-18)
What if the electrostatic law of attraction?
Opposite charges attract
Same charges repel
What are the 4 types of bonds
Covalent
Ionic
Intermetallic
Coordinate covalent
What type of cells generate light
Photocells
Good conductors have how many electrons in valance orbit
3 or less
3 main components to a three phase principle
120 degrees between coils and wavelengths
115v between 1 phase and neutral
200v between 1 phase and another phase
What is electron emission
The superstation of electrons from a metal bonding. It’s a common method of doing this by heating
What is the charged rate of lead acid
2v
What is the charged rate of nickelncadminium
1.2v
How does pressure produce heat
Crushing piezo crystal
How do you increase voltage
Increase magnetic speed strength
Increase movement speed
Length of conductor
Difference between primary and secondary cells
Primary cells aren’t rechargeable whereas secondary are
What’s the charged and discharged voltage of lead acid
Charged - 2v
Uncharged - 1.83v
What’s the charged and discharged voltage of nichel codmium
Charged - 1.2v
Discharged 1v
What’s the most common secondary cell
Lead acid and nickel codium
What’s the mix of the electrolyte consist of and percentage
70/30
Suphric acid and water
Advatanges of using a nickel codium battery over a lead battery
Larger capacity
Better power to weight ratio
Voltage
The difference in energy between electrical charges or potentials.
The force that acts on electrons cause to move
What happens when the distance between the electron and nucleus gets bigger
The stronger the potential energy of electron gets.
What is direct current
If voltage has the same polarity over time. Either positive or negative. Doesn’t change - singular direction
What is a voltmeter
Is connected in parallel with the terminals of a power source.
Two ways to measure voltage
Analogue meter - pointer deflection
Numerical read out - digital meter
What does 1v equal
1000mv
What is electrical current
The flow of electrical charges in a certain direction
What’s the equation for current
Current = charge / time or current = volt/ resistance
Is an electrical current a flow of electrons
No not necessarily. There are other charge carriers that cause the flow of electrons
-in solid conductive materials - electron currents
What’s is dc
Direct current - the charge carriers constantly flow in same direction at same current
What is ac
A flow of charges repeadily changing direction and current in a certain period of time
1 ampere =
1 ampere = 6.24 x 10 (18) electron/second
How do you measure a current of a series
The charge carriers flow through a Ammeter or current meter
What’s is resistance
A measure of the opposition to the current flow of an electrical circuit
What is resistance
Measure of its opposition to the flow of electrical current. The breaking action of a conductive material, therefore dependent on atomic density of material. - closer the ions are the greater the braking action
What is ohms law
The relationship between current, voltage and resistance
What is the ohms law equation
Volatage = current x resistance
What is conductance
The ease with which electric current flows through materials
Conductance
Higher resistance = lower conductivity
Lower resistance = higher conductivity
What’s is the equation for resistance
G = 1/R measured in siemens (s)
What is charge
The sum of all electrical charges is the quantity of electricity - called charge
What’s is the si unit for charge
Coulomb (C) 1c = 6.24 x 10(18) electrons
What’s is the equation for charge
Charge = current/time
What is conventional current flow
The electric current flows from positive to negative pole
Electron flow
direction of electrons is flowing through a conductor depends on applied voltage. If the polarity of the voltage is not changing then electrons will flow through the same direction - DC
If changing polarity then it’s - AC
How does light generate electricity
By a photocell
Semi conductor materials
Silicon and germanium
What is a photocells function
Generates electric voltage as they are energy converters
What effects the amount of electricity generated by a photocell
Time, intensity,colour, type
What’s the device called for recording oscillations?
Oscilloscope
What’s gas discharge
Electrical continuity is gases or metal vapour which results in light
What’s the liquid called in electrolysis
Electrolyte
How do you get current density
Current/cross sectional area
What are the two types of voltage and what’s the difference
Ac- changes polarity
Dc- same polarity
Whats the charge of 1 amp
6.24 x 10 to power of 18
Speed of movement of charges depends on
Temp, cross sectional area, conductor material
How does current density affect heat
The greater the current density, the higher the heat
Whats EMF
Electromotive force
What’s a generator
A device that splits/separates charges
What’s si unit of charge
Columbs
How’s static electricity produced
Contact, friction, induction
What are thermocouples used for in aviation
Measuring exhaust gas temps
What’s the Most common thermocouple
Chromel and alumel
What’s the positive and negative plates of nickel cadmium made up from
Positive plate is made up from nickel oxy hydroxide
Negative plate is made up from metallic cadmium
What does the positive and negative plates of lead acid consist of
Positive is made up from lead peroxide
Negative is made up from spongy lead
In a series cell what happens to volts and amps
Volts increase and Amps stay the same
What determines amount of voltage generated through induction
Magnetic field strength, length of wire, speed of motion
What’s the action called that occurs in a battery cell
Galvanic cell
Advantages of using nickel cadmium batteries over a lead battery?
Larger capacity, better power to weight ratio
What’s the mix of the electrolyte in lead acid
70 percentage sulphric acid
30 percentage water
Most common secondary cell
Lead acid and nickel cadmium
What’s the charged and discharged voltage of nickel cadmium
Charged 1.2
Discharged 1
What’s the charged and discharged voltage of lead acid
Charged 2
Discharged 1.83
Difference between primary and secondary cells
Primary’s are one use and can’t can’t be recharged whereas secondaries can
How do you increase voltage
Increase magnetite strength, increase movement strength, length of conductor
How does pressure produce heat
Crushing the piezo crystal
What’s the electrostatic law of attraction
Opposite charges attract whereas same charges repell
Charges of an electron?
-0.1602 x 10 to the power of minus 18
What types of cells generate light
Photocells
If dc’s applied to water what’s generated at either pole
Negative- hydrogen
Positive- oxygen
4 types of bonds
Inter-metallic, covalent, ionic, coordinate convalent
What’s doping
Adding foreign atoms
Examples of insulators
Porcelain
