8404891
| Question | Answer |
| Closed Mesh | A path that starts and finishes at the same node without crossing over itself |
| Branch | A path that joins two nodes together, must go through at least one element |
| Node | Point 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. |
| Useful Nodes | Nodes with at least 3 branches connected to them |
| Ideal voltage sources | Don't change magnitude or polarity regardless of how much current is being drawn |
| Current source | The direction and magnitude of current flow through a current source is fixed |
| Conventional Current | Assumes charge carriers are positive, flows from positive to negative |
| Ohm's Law | V = I*R |
| Conductance (G) | G = 1 / R |
| Kirchhoff's First Law (KCL) | The algebraic sum of currents entering and leaving a node is zero. "What flows in, must flow out". |
| Kirchhoff's Second Law (KVL) | In a closed mesh the algebraic sum of the element voltages' is zero. |
| Joule's Law | Heat produced in a resistor when current flows through it is proportional to I^2 * R * t Constant of proportionality = 1 if using SI units |
| Power | Rate of work done P = W / t |
| Resistors 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 |
| Combining resistors in series | Add them together |
| Resistors are in parallel when... | ... they are connected to the same two nodes |
| Combining resistors in parallel | The 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 |
| A resistor is short circuited when... | ... each side of the resistor is connect to the same node |
| Voltage Divider | When resistors are in series, V(R1) = V(S) * R1/R1 + R2 |
| Current Divider | When two resistors are parallel, I(1) = I(S) * R2/R1 + R2 This equation only works when there are two resistors |
| Voltage sources in series | Can be added together algebraically to create one source |
| Voltage sources in parallel | Identical sources - Only increases lifespan of source Non-identical sources - Cannot be done |
| Current sources in series | Identical sources - Have no purpose Non-identical sources - Can't be done, breaks KCL |
| Current sources in parallel | Can be algebraically added to form one source |
| Source transformations Voltage source => Current source | Source 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 |
| Source transformation Current source => Voltage source | Source 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 |
| Superposition principal | Current 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 |
| How do you "turn" a voltage source to zero? | Replace it with a short circuit |
| How do you "turn" a current source to zero? | Replace with an open circuit |
| When does maximum power transfer occur? | When the load resistance is equal to the source resistance |
| Maximum power transfer equals? | P = V^2 / 4R (Refer to notes for derivation) |
| Thevenin's equivalent circuit | 1. 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 |
| Norton's equivalent circuit | 1. 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 |
| How are Norton's and Thevenin's equivalent circuits related? | You can move between the two by doing a source transformation |
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