Flashcards
DC Circuits
Cards in this deck (34)
- 1Closed MeshA path that starts and finishes at the same node without crossing over itself
- 2BranchA path that joins two nodes together, must go through at least one element
- 3NodePoint on a circuit where elements meet, can be denoted by a dot or a big loop. It doesn’t matter where they are on the connecting wires just that the node is in between two elements.
- 4Useful NodesNodes with at least 3 branches connected to them
- 5Ideal voltage sourcesDon't change magnitude or polarity regardless of how much current is being drawn
- 6Current sourceThe direction and magnitude of current flow through a current source is fixed
- 7Conventional CurrentAssumes charge carriers are positive, flows from positive to negative
- 8Ohm's LawV = I*R
- 9Conductance (G)G = 1 / R
- 10Kirchhoff's First Law (KCL)The algebraic sum of currents entering and leaving a node is zero. "What flows in, must flow out".
- 11Kirchhoff's Second Law (KVL)In a closed mesh the algebraic sum of the element voltages' is zero.
- 12Joule's LawHeat produced in a resistor when current flows through it is proportional to
I^2 * R * t
Constant of proportionality = 1 if using SI units - 13PowerRate of work done
P = W / t - 14Resistors are in series when...... they are in the same mesh and neither can be found in another mesh without the other one. This can also be seen as there will be a redundant node between the two resistors
- 15Combining resistors in seriesAdd them together
- 16Resistors are in parallel when...... they are connected to the same two nodes
- 17Combining resistors in parallelThe inverse of the total resistance is equal to the sum of the inverse resistances. For two resistors in parallel the total resistance is the product / sum
- 18A resistor is short circuited when...... each side of the resistor is connect to the same node
- 19Voltage DividerWhen resistors are in series,
V(R1) = V(S) * R1/R1 + R2 - 20Current DividerWhen two resistors are parallel,
I(1) = I(S) * R2/R1 + R2
This equation only works when there are two resistors - 21Voltage sources in seriesCan be added together algebraically to create one source
- 22Voltage sources in parallelIdentical sources - Only increases lifespan of source
Non-identical sources - Cannot be done - 23Current sources in seriesIdentical sources - Have no purpose
Non-identical sources - Can't be done, breaks KCL - 24Current sources in parallelCan be algebraically added to form one source
- 25Source transformations Voltage source => Current sourceSource must be in series with a resistor.
Resistor value doesn't change.
Current source magnitude is V / R
Arrow points to +ve terminal of voltage source - 26Source transformation Current source => Voltage sourceSource must be in parallel with a resistor.
Resistor value doesn't change.
voltage source magnitude is I * R
+ve terminal is where the arrow points to - 27Superposition principalCurrent through, or voltage across, any element of a network is equal to the algebraic sum of the currents or voltages produced independently be each source
- 28How do you "turn" a voltage source to zero?Replace it with a short circuit
- 29How do you "turn" a current source to zero?Replace with an open circuit
- 30When does maximum power transfer occur?When the load resistance is equal to the source resistance
- 31Maximum power transfer equals?P = V^2 / 4R
(Refer to notes for derivation) - 32Thevenin's equivalent circuit1. Find open circuit voltage. This will be the voltage of the source
2. "Turn" all sources to zero and find the resistance between the terminals. This will be the equivalent resistace - 33Norton's equivalent circuit1. Find short circuit current entering terminal. This will be the magnitude of the current source
2. "Turn" all sources to zero and find the resistance between the terminals. This will be the equivalent resistace - 34How are Norton's and Thevenin's equivalent circuits related?You can move between the two by doing a source transformation
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- Engineering (16ELA001 - Circuits) Flashcards on DC Circuits, created by Ben Evans on 03/04/2017.
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- Ben Evans
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