Electrical Fundamentals Flashcards
(180 cards)
1
Q
What is a proton?
A
Positively charged particle found in the nucleus
2
Q
What is a neutron?
A
A neutron is a neutrally charged particle found in the nucleus
3
Q
What is the neutrons job in the nucleus?
A
To ensure that the positively charged protons in the nucleus do not repel
4
Q
What are electrons?
A
Electrons are negatively charged particles that travel around the shells placed around the atoms nucleus
5
Q
What prevents the electrons from moving away from the atom?
A
To prevent the electrons from moving away from the nucleus, they are attracted towards the positively charged protons.
6
Q
What force pulls the electrons away from the nucleus?
A
Centrifugal force
7
Q
What is the charge of a single electron?
Units?
A
- 0.1602 x 10^-18
Units : Coulomb (C)
8
Q
What is the charge of a single proton?
Units?
A
0.1602 x 10^-18
Unit : Coulomb (C)
9
Q
What causes an atom to be electrically neutral?
A
Amount of protons in the nucleus is equal to the amount of electrons orbiting the atom
10
Q
What charge does an atom have if it is electrically neutral?
A
Zero
11
Q
If there are more electrons orbiting the nucleus than protons, what is it called?
What charge does it have?
A
An ion
Negative charge
12
Q
What is a charged atom known as?
A
An ion
13
Q
What is a cation?
A
Positively charged ion
14
Q
What is an anion?
A
Negatively charged ion
15
Q
What is valence?
A
Bonding
16
Q
What electrons can be bonded?
A
Valence electrons
17
Q
What are the 3 different types of bonding?
A
Covalent
Ionic/electrovalent
Metallic
18
Q
What type of bonding is used to combine molecules?
A
Covalent
19
Q
Ionic compounds are held together by what bonding?
A
Electrovalent
20
Q
Intermetallic compounds are held together by what bonding?
A
Metallic
21
Q
What is needed for a substance to be a good conductor?
A
More free electrons to allow easy current flow
22
Q
If you add more potential difference to a substance and there are more particle collisions, is it a conductor, semi conductor or an insulator?
A
Insulator
23
Q
What makes a good conductor?
A
When the substance has a high mobility of electrons
24
Q
If you increase the potential difference in a conductor, what happens to the charge and current?
A
Increase in charge and current
25
Describe the structure of the electrons in an insulator
Electrons in an insulator are tightly connected to the atoms which prevents them from breaking away (very little or no free electrons)
26
Is a pure semi conductor a good conductor?
No
27
What conditions can increase conductivity in a semi conductor?
Heat, light and doping
28
What is doping?
Adding a foreign atom to the substance
29
What are examples of conductors?
Copper
Silver
Gold
Aluminium
30
What are examples of semi conductors?
Silicon
Germanium
Carbon
31
What are examples of insulators?
Rubber
Mica
Porcellain
32
If a semi conductor is heated, what happens to its resistance?
Resistance decreases
33
If a metals resistance increases, what could be the reason why?
The metal has been heated up
34
How does a semi conductors resistance decrease if heat is applied?
More kinetic energy in the particles which weakens the bonds so when potential difference is applied, current can be created
35
How can you separate charges?
Electrolysis
| Rub one substance against another
36
When rubbing one substance with another, it is best for the substance to be a conductor, semi conductor or insulator?
Insulator
37
What is does the position of electrons tell you?
How much energy the electron possesses
38
If the electron is placed further away from the nucleus, what does that mean?
Electron has a weaker bond
39
Why does an electron have a weaker bond if it is on a shell further away from the nucleus?
It has less of a force pulling it towards the nucleus from the protons as it is further away
40
How does light in a gas come about?
Force free electrons to collide with an electrons of an atom
The electron in the atom gains energy from the collision, moves to a higher state of energy
Not stable in that shell so it needs to lose energy to return to its stable state
To lose energy it releases a photon
41
What method is used to conduct a liquid?
Electrolysis
42
What is the unit of charge?
| What is the value of 1 unit of charge?
Coulombs
6.24 x10^18 electrons
43
Define Ampere
The rate of flow of charge
Charge per second
44
What is the equation for Current?
Units?
I = Q / t
Unit: Amps
45
Cations will move towards?
Cathode
46
Anions will move towards?
Anodes
47
What does V, I, Q and R stand for?
Potential difference
Current
Charge
Resistance
48
What is the unit of potential Difference?
Volts (V)
49
What is the unit for Current?
Amps (A)
50
What is the unit for charge?
Coloumbs (C)
51
What is the unit for Resistance?
Ohms
52
What is resistance?
The opposition to current flow
53
What corrodes - anode or cathode?
| When does it stop corroding?
Anode
| Corrodes when it reaches the Amp hour capacity
54
What sort of air produces more static charge?
Cold, dry air
55
What is the difference between flux and electrostatic lines?
Flux lines are loops
| Electrostatic lines are straight
56
What is the flow in solids?
Electrons
57
What is the flow in liquids?
Ions
58
What is the flow in a gas?
Electrons and ions
59
If there is more resistance, what also increases?
The power needed for current to pass
| Heat increases
60
What is in a vacuum?
Nothing
61
What needs to be present for conduction to take place?
Charge
62
What must you do to create conduction in a vacuum?
Create a charge
63
What is thermionic emission?
The process of heating up the cathode/anode to give up electrons through collision
64
What are electrostatic plates?
Plates that repel/attract electrons to point them in the direction to hit the object at a certain point and time
65
What is always present if a current flows in a solid, liquid or gas?
Heat
| Magnetism
66
What else could be a by-product of the current flow in the states of matter?
Light in some gases
Chemical effect in liquids (electrolysis)
Effect in humans e.g shock
67
What does the current flow depend on?
How much resistance there is
68
Define the job of a fuse
A safety device consisting of a strip of wire that melts and breaks an electric circuit if the current exceeds a safe level
69
Define the job of a circuit Breaker
Automatic device for stopping the flow of current in an electric circuit as a safety measure
70
What is the equation for resistance?
Resistance = Voltage / Current
71
What is the equation for voltage?
Voltage = Current x Resistance
72
What is the ohm’s law equation for current?
Current = Voltage / Resistance
73
What is the inverse of resistance?
Conductance
74
What is the symbol and units of conductance?
Symbol : G
Unit : Siemens
75
What is the equation for current density?
Units?
Current Density = Current /Cross-Sectional Area
J= I/A
Units: A/mm^2
76
Is the cross sectional area of a conductor is smaller, what happens to the current density?
Current density increases
77
How do you know if the current density is increasing?
It is producing more heat
78
What is a hotspot?
When the conductor is damaged, it creates a hotspot. That hotspot means there is a smaller cross sectional area which means the current flows through the smaller cross sectional area which increases the heat
79
What does current density depend on?
Current density depends on
The material of the wire
The Cross Sectional Area of the wire
The possible methods of cooling
80
What is the typical maximum heat of a cable?
60 degrees celcius
81
What is potential difference?
The voltage from one point compared to another
82
What is the unit of potential difference?
Volts
83
What must potential difference be measured in?
It must be messured in a parallel circuit
84
What sort of resistance does a voltmeter have and why?
High resistance
So the voltmeter doesn’t draw the current through it
85
How can you get a negative voltage on the voltmeter?
If you connect the wires so that it measures electron flow rather than conventional current
86
What is the definition of current?
The rate of flow of charge
87
How do you measure the current?
The Ammeter must be in series with the circuit
88
Can you get a negative reading on the ammeter?
Yes
89
What resistance must the ammeter have and why?
It must have a low resistance to avoid significant alteration with the current it is measuring
90
What are the different types of generation of electricity?
```
Light
Heat
Friction
Pressure
Chemical Action
Magnetism
```
91
What do you get if light hits certain semi conductors?
Charge separation
92
What does the conductivity of a semi conductor depend on?
How much doping was made
93
What is doping?
The addition of foreign atoms to create impurities in the substance
94
During the breaking of bonds, what is released?
An electron and a hole
95
What is the positive charge carrier?
The hole
96
What causes the bonds to break between in an atom and conductance to happen?
The vibrations of atoms from heat
97
What is the depletion layer?
The area at which charge is not present due to charge separation of light
98
In light generation, what does voltage depend on?
The light intensity, the kind of light and the type of depletion layer
99
What does the kind of light indicate?
The frequency and the amount if energy the light possesses
100
What is the typical Voltage and Power light generates?
Voltage : 0.6V
Power : 10mW per cm^3
101
What is a thermocouple?
Thermocouples are devices used to measure temperature
102
What is a thermocouples range?
-200 degrees Celcius to 2300 degrees Celcius
103
How does a thermocouple work?
What effect is this?
A thermocouple uses 2 dissimilar metals joined at the elds. One material has more free electrons than the other and when heated at one end, the atoms are forced to give up electrons which produces a current. This causes charge separation which generates a voltage.
This is the Seebeck effect
104
What is the thermocouple we mainly use and its Voltage per 100 degrees C?
Chromel - Alumel
4.2 mV per 100 degrees Celcius
105
What does a greater heat distance mean for current?
Current is greater too
106
How does friction generate voltage?
If an insulator is rubbed, electrical charges separate and voltage is generated
107
What type of material produces a static charge when it is rubbed?
An insulator
108
The voltage can reach up to a few .......... during friction
kV
109
If two bodies have a different charges between them, what is present?
Voltage
| An electrical field between the two bodies
110
How does excitation happen ?
When you put pressure on a crystal
111
What does a small amount of pressure on a crystal produce?
Small sounds
112
What does a greater vibration result in?
A greater Voltage
113
If a Piezo Crystal is deformed through pressure it generates what?
Voltage
114
The generation of voltage through deforming a Piezo Crystal through pressure is what effect?
Piezoelectric effect
115
Give an example of where Chemical Action is used to obtain a voltage
Batteries
116
How does Chemical Action work?
Chemical Action uses 2 different types if metals immersed into a conducting electrically conducting liquid. Ions move from positive to negative and the charge separation using the electrodes generates voltage
117
What is a voltage generator called?
Galvanic cells
118
What do galvanic cells consist of?
Electrolyte and electrodes
119
What causes an electrical voltage in a liquid?
Electrochemical reactions
120
If a metal has a highly negative voltage, what happens to it?
It is consumed and dissolves
121
Give 2 DC sources of electricity
Primary Cells
| Secindary Cells
122
What is the difference between primary and secondary cells?
Primary Cells - immediately supplies voltage without the need to charge beforehand and it is irreversible
Secondary Cells - rechargeable and either lead acid/ nickel cadmium construction.
123
What is the charged and final discharge voltage of lead acid cells?
When charged voltage = 2V
Final discharge voltage = 1.83 V
124
What are the positive plates filled with in a lead acid cell?
Lead peroxide
125
What are the negative plates filled with in a lead acid cell?
Pure (spongey) lead
126
What is the electrolyte liquid in a lead acid cell and their percentages?
```
Sulphuric Acid (30%)
Water (70%)
```
127
How does a lead acid battery operate?
The current flows through the electrolyte and ions are formed from the solutions i.e, the sulphuric acid turns into hydrogen ions and sulphur ions. The ions carry a positive and negative charge and move towards the attracting plates. This creates charge separation which generates voltage. The ions continue to coat the plates in a different material to a point where ions have little to no attraction to the plates. This skows down the reaction
128
If the reaction on a lead acid cell stops completely what happens?
Reverse polarity - it has discharged too much voltage
129
How does a lead battery recharge?
An external power supply is added and it forces ions off the plates and into the electrolytes
130
What is the difference between a battery and a cell?
A cell is a single unit that converts chemical energy into electrical energy
A battery is a collection of cells
131
In a secondary cell, what does current depend on?
The size of the plates
132
In a secondary cell, what does voltage depend on?
The material of the conductor
133
What is a benefit and a disadvantage of using lead acid cells over nickel cadmium cells?
It is cheaper but it is less effective
134
What is the positive plate in a nickel cadmium cell?
Nickel Oxyhydroxide
135
What is the negative plate in a nickel cadmium cell?
Metallic Cadmium
136
What is the electrolyte in a nickel cadmium cell?
Potassium Hydroxide
137
What is internal resistance?
The electrical resistance inside power supplies that can limit the amount of potential difference supplied to the load
138
What does internal resistance do?
Causes the terminal voltage to drop
139
What is the terminal voltage?
Terminal voltage is the voltage output measured at two terminals of a device
140
What happens to the terminal voltage when you add more load to the circuit?
Terminal voltage drops
141
What must the circuit be fir the terminal voltage to equal the source voltage?
Must be an open circuit
142
What is annopen circuit?
When the generator does not supply to anything
143
What is the source voltage?
The voltage supplied by the material
144
How do you add internal resistance in a SERIES circuit?
Add similar voltage
145
Putting batteries in parallel does what to the current, resistance and voltage?
Current increases, resistance decreases and voltage stays the same
146
Putting batteries in series does what to voltage, resistance and current?
Increases voltage and resistance and decreases the current
147
When can induction with a conductor take place?
When a magnet is in movement, and cuts through flux lines
148
What do conductors do to magnetic fields and why?
Able to skew magnetic fields because they want to take the easier route. Going through the conductor is easier than travelling through air
149
What symbol do we use when current is going towards us?
A dot
150
What symbol do we use when a current is going away from us?
A cross
151
How is current produced in a magnetic field?
The relative movement of the conductor through the magnetic field causes current
152
When would you get the most current?
When the conductor cuts through the most flux lines
153
How do you get more current in a magnetic field?
More voltage = more current
154
Where would the most induction take place?
When the conductor is directly above the South and Below the North magnet
155
What does voltage rely on for a magentic generation of electricity?
The flux density
The length of the coil
The velocity if the turning effect of the conductor
156
How would you get more voltage in a magnetic generation of electricity?
Flux density gets stronger
Length of conductor increases
Velocity of the turning effect of the conductor increases
157
What is the unit of frequency?
Hertz
158
What is frequency?
The rate at which something occurs over a period of time
159
What is the equation for frequency?
Frequency = 1/ time
160
What types of AC graphs are there?
Sinusodal
Square
Saw tooth
Triangular
161
How do you know via a graph if it is an AC circuit?
The graph goes through negative components too
162
What is an AC supply also known as?
Sinusodal Supply
163
How do you find the RMS?
Peak Voltage x 0.707
164
What is the equivalent value for voltage in DC and AC and what does it mean?
240V
The 240VRMS in an AC circuit has the same heating value as a 240VDC circuit
165
What is the name for the time taken for a complete cycle to happen?
Period
166
What is the term for an AC circuit and DC circuit overlaying?
Superimposed voltage
167
If all 3 phases have the same loading and 0 phase shifts, what is the neutral line?
0V from the neutral line, nothing is flowing from it
168
If there is an imbalance in the 3 loads but 0 phase shifts, the neutral line has..,
Current flowing in the neutral line equal to the current in phase one of the generator
169
If there is an imbalance in the 3 loads and a phase shift, the neutral line ...
Has current flowing through it with the value of two phase currents
170
What is braking action?
The level of resistance in a circuit
171
What is braking resistance dependent on?
The atomic density of the material
172
What is a optoelectic component called?
Photocells
173
What is a photon?
Particle component of light
174
What is light irradiation?
The kight inout to break bonds
175
What is electron emission?
The separation of electrons in a metallic bond
Sometimes due to light
176
What does the direction of the flow of electrons depends on?
The polarity of the applied voltage
177
When in a Nickel Cadmium battery is the electrolyte level at its lowest?
After discharge
178
What is the discharge value for Nickel Cadmium Cells?
1 Volt
179
What happens to current in a series circuit when load increases?
Current decreases
180
What is the average voltage equation?
Voltage average = sum of all mid ordinates / all mid ordinates
