# Syed's Mid-Term exam Cheatsheet (ECE)

## Lecture 1

nothing special really

## Lecture 2





periodic function is one that satisfies:

sinusoidal voltage:

some relations to it:

for my reference: Voltage drop is the decrease of electrical potential along the path of a current flowing in an electrical circuit.

## Lecture 3 (this ig is excluded from the syllabus)




## Lecture 4

ohms law:




Conductance (measured in siemens, S):


Power:


Resistors connected in series:

## Lecture 5

Resistors connected in parallel:

or



Voltage division rule:


Current division rule:

branches, loops and nodes (network topology):

## Lecture 6
Kirchhoff’s Current Law (KCL):


sum of incoming currents = sum of outgoing currents (relative to a node)

Kirchhoff's Voltage Law (KVL):


sum of voltage rise = sum of voltage drop (relative to a loop)

## Lecture 7

only solved questions, no new concepts

## Lecture 8

Voltage sources relation:


Current sources relation:


Source transformations:



## Lecture 9

To Find RTH:

1. Find that portion of the network across which the Thevenin equivalent circuit needs to be found.
2. Load resistor RL is temporarily removed from the network.
3. Mark the terminals of the remaining two-terminal network (say A and B).
4. Identify all voltage and current sources and retain their internal resistances if any.
5. Replace the voltage sources by short circuits.
6. Replace the current sources by open circuits.
7. Find the resistance between terminal A and B.

The resistance between A and B is called as Thevenin’s resistance RTH

To Find VTH:

1. In the original circuit, remove the load resistor (RL) connected between the marked terminals (A and B).
2. Find the open-circuit voltage (VTH) between the marked terminals (A and B). VAB is Thevenin voltage, denoted by symbol VTH.
3. Draw the Thevenin equivalent circuit by keeping VTH, RTH and the load resistor (RL) in series

## Lecture 10

Thevenin's, Thevenin's and Thevenin's and nothing new

## Lecture 11

Norton's now

To Find RN:

1. Remove that portion of the network across which the Norton’s equivalent circuit needs to be found.
2. Load resistor RL is temporarily removed from the network.
3. Mark the terminals of the remaining two-terminal network (say A and B).
4. Identify all voltage and current sources and retain their internal resistances if any.
5. Replace the voltage sources by short circuits
6. Replace the current sources by open circuits
7. Find the resistance between terminal A and B

The process of finding RTH and RN is exactly same. Hence RTH = RN

To Find IN:

1. In the original circuit, short the load resistor (RL) connected between the marked terminals (A and B).
2. Find the short-circuit current (IN) through the marked terminals (A and B).
3. IN is called as Norton’s current source.
4. Draw the Norton’s equivalent circuit by keeping IN, RN and the load resistor (RL) in parallel.

## Lecture 12

Went over superposition theorem a little then sir ended early because it was supposedly a holiday

## Lecture 12 (again)

Definition just in case because it had no equations:

Superposition theorem states that the current through, or voltage across, an element in a linear
bilateral network is equal to the algebraic sum of the currents or voltages produced independently
by each source.

Steps:

1. Turn off all independent sources except one. Find the output (voltage or current) due to the active
source.
2. Repeat step 1 for each of the other independent sources.
3. Find the total output by adding algebraically all of the results found in steps 1 & 2 above.

Maximum power transfer:


 when RL = R

## Lecture 13

Nodal analysis:

1. Select a node as the reference node. Assign voltages v1, v2, . . . , vn−1 to the remaining (n − 1) nodes. The voltages are referenced with respect to the reference node.
2. Apply KCL to each of the (n − 1) nonreference nodes. Use Ohm’s law to express the branch currents in terms of node voltages.
3. Solve the resulting simultaneous equations to obtain the unknown node voltages.

Mesh analysis:

1. Assign mesh currents i1, i2, . . . , in to the n meshes.
2. Apply KVL to each of the n meshes. Use Ohm’s law to express the voltages in terms of the mesh currents.
3. Solve the resulting n simultaneous equations to get the mesh currents

OK THATS ALL