Electricity Textbook Goodnotes Recap Flashcards
Current?
Rate of flow of charge in a circuit and is measured in amperes
Charge?
What is carried through wires by electrons and is measured in coulombs
Charge equation?
Charge = Current x Time
ΔQ = I x ΔT
Coulomb?
The amount of charge that passes in one second per ampere of current
Current Measurement?
Current is measured using an ammeter which has to be placed in series
Power Source?
What allows electric charge to flow through a circuit due to energy being transferred to the charge
Electric Potential Energy?
When charge flows through a power source its raised through a potential as the energy is transferred to the charge
Work Done?
Another name for work done is energy transferred and is what a power source uses to move charge around the circuit
Potential Difference?
Where work done moves a unit of charge between 2 points and has the unit of volts
Potential Difference equation?
V = W / Q
Potential Difference = Work Done / Charge
Volt?
1 joule of energy being converted to move 1 coulomb of charge through a circuit or component and also has the unit name of joule per coulomb
Voltmeter?
What is used to measure the potential difference of an electrical component and has to be set up in a parallel configuration with the component being measured
Current and Potential Difference relationship?
When an electrical component has a potential difference it will cause current to flow around a circuit but the amount of current it receives depends on the components resistance
Resistance?
The measure of opposition to get current to flow through a component or circuit and is measured in ohms which has the symbol Ω
Ohm?
A component has a resistance of 1 ohm if 1 volt causes 1 amp to flow through a circuit
Resistance Equation?
R = V / I
Resistance = Potential Difference / Current
Ohm’s Law?
When current and potential difference have a directly proportional relationship creating a straight line relationship on a graph and is only true for ohmic conductors under constant physical conditions
I-V characteristics?
Show how current flowing through a component changes as the potential difference across a component changes
I-V characteristics relationship with resistance?
The shallower the gradient produced the greater the resistance of the component. Resistance is the negative reciprocal of the gradient of the graph produced. A curved gradient means resistance is not constant for the component.
Ideal Voltmeter?
Infinite resistance meaning no current is able to flow through it
Ideal Ammeter?
No resistance or potential difference
Ohmic Conductor results?
The current has a directly proportional relationship with voltage under constant physical conditions with resistance being constant as its the gradient
Ohmic Conductor example?
An example of an ohmic conductor is a metallic conductor
Filament Lamp I-V characteristics?
A curve that starts steep but gets shallower as the voltage rises and curves in the opposite direction when in the negative axis
Filament?
A thin coil of metal wire that has a different trend to ohmic components as the temperature increasing causes the resistance to increase
Heat on Filament Components?
When the current flows some of the electrical energy is converted into heat which causes the metal filament to heat up. The additional heat energy causes the particles in the metal to vibrate more. This makes it harder to get through the resistor causing current to decrease and resistance to increase.
Diode?
Made from semi-conductors and are designed to let current flow in a singular direction
Forward Bias?
The direction in which current is allowed to flow as a result of it passing through a diode
Threshold Voltage?
Most diodes require a threshold voltage of 0.6 V and is the voltage required before a diode will conduct electrical energy and is the x-axis intercept on an i-v characteristic graph
Reverse Bias?
The resistance is very high and the current that is allowed to flow through is of a minimal amount
Diode I-V Characteristics?
Up to its threshold voltage the current is just below zero but after its been achieved it increases exponentially
What factors affect resistance?
Length, area, resistivity
Length affecting resistance?
The longer the wire the more difficult current is able to flow through it due to resistance and length having a directly proportional relationship with length
Area affecting resistance?
The wider the wire the easier it is for electrons to pass along causing resistance to decrease and is why cross-sectional area and resistance have an inversely proportional relationship
Resistivity?
Has the symbol ρ and the units of Ωm and is a property of a material that is the measure of how much a material resists the flow of current
Resistivity factors?
The structure of the material and environmental factors like light and temperature
Resistivity definition?
The resistance of a 1m length of wire with a width of 1 m^2 cross-sectional area
Resistivity trends?
The lower the resistivity the better it is at conducting electricity
Resistivity equation?
ρ = RA / L
Resistivity = (Resistance x Cross-Sectional Area) / Length of wire
Semi-Conductors?
A group of materials that have fewer charge carriers available and as a result are poor at conducting electricity
Semi-conductor purpose?
If energy is supplied to a semi-conductor more charge carriers can be released which means the resistivity of a material decreases
Semi-conductors uses?
They make excellent sensors for detecting changes in the environment so examples include diodes, thermistors, light dependent resistors
Thermistor?
A component with a resistance dependent on temperature
NTC?
Stands for Negative Temperature Coefficient and is the main type of thermistor
NTC thermistor function?
Resistance decreases when temperature increases and this environmental change causes electrons to have enough energy to escape from their atoms which means more charge carriers are available which lowers resistance
NTC thermistor graph?
It has an exponential shape with the line curving away from the origin as it shows a directly proportional relationship with temperature increasing the resistance
NTC thermistor uses?
Temperature sensor, temperature controller for a water bath, in combination with an ammeter to show resistance and temperature relationship
Thermistor Test?
Place a thermistor into a beaker of boiling water and cover it. Measure and record the water temperature, current on the ammeter and check potential difference is constant at 5 degrees Celsius intervals. Calculate resistance with results and plot results on a temperature-resistance graph
General Resistance Trends?
Every metal will have resistivity and the resistance they have is when electricity flows some electrical energy is wasted in the form of heat
Transitional Temperature?
Resistivity disappears entirely making the material a superconductor as a result of lowering resistivity below a specific temperature
No resistance trend?
No resistance on a circuit means none of the electrical energy in the circuit is converted into heat which means there is no wasted energy
Normal conductors critical temperature?
-263 Degrees Celsius
10 Kelvin
1 Kelvin to Degrees Celsius?
-273 Degrees Celsius
Superconductor uses?
Power Cables, Electric Circuits, Strong Electromagnets
Resistivity method?
Measure and calculate the cross-sectional area of the wire. Attach a flying lead to a test wire and measure the distance of wire it covers. Close the switch and record current and voltage values of the circuit and then open the switch. Repeat this at different flying lead intervals. Calculate resistance and plot a resistance-distance graph
Resistivity Result Gradient?
On a resistance (y-axis) and distance (x-axis) graph the resistance / change in length is the gradient. Multiplying this by the cross-sectional area gives the value of resistivity
Power?
Measured in watts and is the rate of energy transfer
Watt?
1 joule per second being transferred in an electrical circuit
Power Equation?
Power = Energy Transferred / Time
P = E / T
Power = Current x Voltage
P = IV
Charge defining Potential Difference and Current?
Potential difference is the energy transferred per coulomb. Current is the number of coulombs transferred per second. These relationships with charge define power.
Energy Transferred Equations?
E = IVT
Energy = Current x Potential Difference x Time
E = (V^2 / R) x T
Energy = (Voltage ^2 / Resistance) x Time
E = I^2 RT
Energy = Current^2 x Resistance x Time
Internal Resistance?
Electrons colliding with atoms inside a power source
Resistance Occurring?
Electrons colliding with atoms and losing energy after being converted into electrical energy from chemical energy
Load Resistance?
Also called external resistance, this is the total resistance in all the components in an external circuit
EMF?
Has the units volts and stands for electromotive force and is the amount of electrical energy the battery produces and transfers to each coulomb of charge
EMF Equation?
ϵ = E / Q
EMF = Electrical Energy / Charge
Terminal Potential Difference?
It is the potential difference across the load resistance and is the energy transferred when one coulomb of charge flows through the load resistance. If there is no internal resistance it is the same as the EMF.
Lost Volts?
The energy wasted per coulomb to overcome the internal resistance
Load Resistance and Internal Resistance?
The energy per coulomb supplied by the power source is equal to the energy per coulomb wasted in internal resistance and the energy per coulomb wasted in internal resistance
EMF and Internal Resistance equation?
ϵ = I (R + r)
EMF = Current (Internal Resistance + Load Resistance)
ϵ = V + v
EMF = Potential Difference + Lost Volts
Internal Resistance affect on energy?
Some energy is lost when overcoming the internal resistance of a power supply and this is dissipated in the form of heat
Dissipation from power supply equation?
P = I^2 x Resistance
Power in power supply = Current^ x Internal Resistance
EMF practical method?
Use a variable resistor to set the load resistance and have it at its highest reading. Close the switch and record the potential difference and current readings and then close the switch. Decrease the resistance on the variable resistor and and record the readings and do this at regular intervals of resistance. Plot a potential difference-current graph where y-intercept equals EMF and the gradient is the internal resistance
Charge and Current behaviour?
Charge doesn’t get used up or lost. This means the charge flows in and out of a junction in a circuit. Since current is the rate of flow of charge it follows the same behavior.
Gustav Kirchhoff?
German scientist who developed a set of laws for current and potential difference of components.
Kirchhoff’s 1st Law?
The total current entering a junction is the total exiting a junction
Closed System with EMF and Potential Difference?
EMF and Potential difference must be equal in a closed system to allow energy to be conserved when it is transferred from energy to charge by EMF creating a potential difference
Kirchhoff’s 2nd Law?
The total EMF around a series circuit is the sum of the potential difference across the components
Current in Series?
Current in a series circuit is the same at all points
EMF in series?
EMF is split between all the components in series due to Kirchhoff’s 2nd Law
Current in a parallel?
The current is split at each junction so the total current is the sum of the current at the end of the branches added together
Potential Difference in parallel?
The same across all the components
Resistance in parallel?
The resistance in a parallel circuit are 1 being divided by the sum of resistance in each branch being added together and then to the power of -1 to get the total resistance
EMF in parallel?
Each loop of EMF equals the sum of the individual potential differences and all the loops EMF is added to produce a total EMF
EMF in parallel with charge?
Each charge goes through each cell so as a result there is EMF in each component so is why the individual EMF is added together
Identical Cells EMF value in parallel?
For identical cells in a parallel circuit the EMF is the same size as EMF for a single cell. This is because the amount of charge doesn’t increase by adding cells in parallel but this differs with the amount of paths it can take
Identical Cells behavior in parallel?
Current is split equally amongst identical cells and the charge only gains EMF from cells it travels through so EMF doesn’t change
Potential Divider?
A circuit with a voltage source and resistors in a series layout
Voltage in a potential divider?
The potential difference across the voltage source is split across the resistors in a ratio of their resistances
Potential Divider Use?
They can be used to supply a potential difference between zero and the potential difference across the power supply
V out?
The notation of the remaining voltage that can be supplied to another component
Benefit of a Potential Divider?
Useful if a varying potential difference is required or a lower potential difference than the power supply is needed
Vs?
The symbol for a voltage source
Total Resistance of a potential divider?
R = R1 + R2
Vs Formula?
Vs = I (R1+R2)
Potential Divider Equation?
V out = (R2 / R1+ R2) x Vs
Fixed Resistor Compared to Variable Resistor?
A variable resistor in a potential divider allows the voltage output to be adjusted in the potential divider
LDR?
Stands for light dependant resistor and has a very high resistance in low light conditions but a very low resistance in high light conditions
Potential Dividers with environment changes?
An NTC thermistor or a LDR can be used as one of the resistors in a potential divider to allow the voltage output to be able to vary with changes in light or temperature and are useful in circuits using switches
NTC Resistor?
An NTC resistor varies resistance in the opposite direction to a resistor
Potentiometer?
A variable resistor replacing R1 and R2 in a potential divider. It has a slider that can be moved to adjust the relative sizes of R1 and R2 and consequently the output voltage ( V out)
