Basic Principles Flashcards
Describe what a passive component is?
Components without a separate power supply.
Typically Modify Voltage or Current.
Includes resistors capacitors and inductors
Describe what an Active Component is
Components with their own a separate power supply.
Typically adds to the Voltage or Current.
mostly in the form of silicon chips
What does this symbol represent
Connection to Ground
Clamps the negative terminal to the potential of the earth (0v) to create a fixed reference
Define Current
Amount of charge that flows per second due to an electromotive force (voltage)
Amps
Explain why current flows in the opposite direction to the flow of electrons
. Electron gains enough energy to remove itself from its valence orbit
. Leaves behinds a local +ve charge
. An electron that has removed itself from an adjacent atoms valence shell , move into the valence orbit of the original atom. Making the local charge back to neutral
. Repeated Droping and removing of electrons from valence bands causes the positive charge to shuffle along. Creating a flow of charge.
This is current, opposite direction to the movement of electrons
What’s the difference between thermal excitation and applied voltage as ways that cause movement of electrons through wires
Thermal excitation causes electrons to move in random directions
Applied voltages cause electrons to move in a certain direction
Explain and Derive the Equation for Voltage
. Electrons that move across a battery are attracted to the atoms that have lost an electron, due to a difference in charge
. This creates an electrostatic field
Work is done moving the charge a distance within this magnetic field within the battery ,
Potential difference (voltage) is created by moving a charge between 2 points in an Electric field
Define Voltage
the potential energy that is built up per unit charge when a charge is moved against an attractive within an electric field.
Show how Power = Current X Volatge
Explain the Voltage Waterfall analogy
. Current moves from the high potential energy to the low potential energy , potential energy is dissipated as the water falls
Voltage is the pump that moves the water from the low potential to the high potential
Give an explanation to the unit of a volt
Potential difference create when 1 Joule of work is done to move 1 coulomb of charge between 2 points in an electric field
What is impedance
Why is impedance not necessarily resistance
The opposition to the flow of current
Electrical Resistance is a type of impedance, however it is not the sole thing that opposite the flow of current . (electrical Reactance for example)
Explain Electrical Resistance
Collisions between electrons and atoms in a material causing the electrons to loose energy
Dependant on a type of material
Explain Voltage Drops
Voltage/ Potential Energy is dissipated across an impedance as the electrons are loosing energy if a current is flowing.
Voltage is therefore lost and energy is disipated across a component . Causing a “Voltage drop”
What is Resistivity
What’s the Equation?
Measure of how easily charge can flow through a material
What’s the convention of the direction of the flow of current
+ve terminal to a -ve terminal
movement of vacancies (positive charge) in the valence band of the conductors atoms
Explain What Virtual Ground is
Potential difference is the difference in the electric potential of the two terminals
A 555V positive terminal and a 550V negative terminal has the same potential difference as a 5v positive and 0v negative terminal
Electric potential of Earth = 0v , hence when you connect circuit to virtual ground the negative terminal is equal to 0v
What is Kirchhoff voltage law
Sum of all voltage rises in a closed loop is equal to the sum of voltage drops in the same closed loop
Conservation of Energy
What’s the voltage divider equation
Explain a DC Voltage source
Maintains a constant electric potential difference between the positive and negative terminals.
What’s the difference between an ideal and Real Voltage Source?
What’s the formula associated with a Real Voltage Source
Ideal Voltage source has no internal impedance.
Real Voltage Source is modelled as an Ideal Voltage Source and a Resistor.
EMF = I X ( R(internal) + R(Load). )
Where I X R(load) = Terminal Voltage
9 = I1 ( 20+2.5 )
I1 = 0.4 Amps
Terminal Voltage = 0.4 X 20 = 8V
9 = I2 (500+2.5)
I2 = 0.0179 Amps
Terminal Voltage = 0.0179X 500 = 8.95V
if R load»_space;»> R Internal then Terminal Voltage is larger, more voltage dissipated in load then battery
3.3V
Derive the equation for the resistance of the following circuit
What’s the potential difference between A & B
What’s the current in each Branch
1.04V
75 ohm branch = 0.0140 amps
47,50 ohm branch = 0.0108 amps
Total current = 0.0247 amps
34 ohms
Explain Thevenin’s theorem
Any linear circuit can be simplified into an equivalent circuit of a single ideal voltage source and a series resistance.
Find thevenin Resistance
Find thevenin Voltage and Draw Equivalent circuit
what are these symbols representing
And Define it
Current Source
Device that outputs a constant current , ideally independent (unaffected) of the load connected to it
Explain the difference from an ideal and a real current source
Ideal current source outputs a constant current, Voltage rise of the current source increases linearly as Rload decreases.
Real current sources it is not perfectly linear. They are modelled as a High Resistance resistor in parallel to the current source.
Define a node
junction in a circuit where 2 more components are connected
Define a circuit
multiple closed loops of components and generators
define a loop
any internal loop of components including generators
define a mesh
Closed loop/path that doesn’t contain no other loops inside it.
define a network
sum of the connected circuits in an electronic.
Explain Kirchhoff current law
Sum of currents into a node is equal to the sum of currents exiting a node.
Conservation of charge
What’s the Current Divider Equation
Describe Mesh Analysis
Identifying Circulating Currents that flow around the circuits mesh’s
Construct Equations using KVL , including all circulating currents that interact with the mesh.
Solve for Current
Describe Superposition
Calculate the response to only 1 voltage or current source , by replacing all other voltages sources with short circuits and current sources with open circuits
Repeat for other sources
Superimpose the results from each calculation
Use mesh analysis to calculate the following currents
i3 is incorrect decimal
Direction of the mesh’s current you are analysing is always positive
Calculate the Theverin Resistance of the following circuit
5 ohms
Calculate the Theverin Voltage of the following circuit
Rth = 5 Ohms
3v
