ELECTENG 101

Electrostatic force

Attributed to electric charge, is a physical property of matter that causes all matters to experience and exert a force when placed next to each other

Coulomb’s law equation

F proportional to q₁q₂ / r²

Flow of charges

Movement of electrons

Ampere units

Coulombs per second

I_AB

Current flowing from A to B

Current equation

i = dq/dt

current is the derivative of the total number of charges passing a given section over a period of time

Amount of charge equation (from current)

Integral of current equation with time as upper limit

OR Area under a current-time graph

Voltage definition

difference of energy between 2 points per coulomb

Voltage units

Joules per coulomb

What does ‘5V’ actually mean?

One end of a component has 5J of energy more than the other

Voltage arrow tail

The end at which the difference is taken with respect to

Voltage arrow head

End with the higher voltage

V_AB

Voltage of A (arrow head) taken with respect to B (arrow tail)

Common reference point

Define voltages at various points in the circuit by measuring them with respect to this reference point.

When charge flows through a conductor…

It must lose energy due to colliding and repelling from other charges

Amount of energy lost when a charge flows through a conductor is subject to…

How difficult it is for the charges to flow which depends on chemical and physical properties of a conductor

Amount of energy lost is directly proportional to…

The rate at which charges flow through the conductor

More charge through a conductor causes…

More energy to be lost by each charge

‘R’

Constant of proportionality

Ohms law requires

An inherently assumed voltage polarity and current direction

Ohms law current direction

Same direction as voltage drop or opposite that of a voltage arrow

Ohm units

Volts per ampere

Ideal wire

no resistance

Ideal electrical source

Maintains its intended operating behavior with zero variability and can supply / receive infinite amounts of energy

Real sources

Finite energy capacities

Ideal voltage source

Maintains constant voltage across its terminals regardless of how much current is developed through it

Ideal current source

Maintains constant current regardless of voltage

Power (1)

energy supplied or received per second

Power (2)

Rate at which electric charges gain or lose electric potential energy

Current direction under power definition

In the direction of the voltage drop or against the voltage arrow (power received by a component from the circuit)

P = VI (Current and voltage direction)

Current points in opposite direction to voltage arrow (same direction as voltage drop) - Indicated that Power is supplied by the circuit and the component is receiving that power.

P = -VI (Current and voltage direction)

Current points in the same direction as voltage arrow which indicates that the component is supplying power to the circuit.

Kirchoff’s Current Law - Explaination

Behavior of current in a circuit

Kirchoff’s current law - definition (long)

The amount of charge arriving at any point in one second must equal the amount of charge leaving that point in one second.

Kirchoff’s current law - definition (short)

‘The algebraic sum of the currents leaving any node in a circuit must equal zero’.

Node

A point in a circuit where two or more components are connected (physically touching or connected via ideal wire)

Kirchoff’s voltage law - definition (long)

Total voltage rises around a loop in a circuit must equal the total voltage drops in the same loop

Kirchoff’s voltage law - definition (short)

The algebraic sum of voltage rises around a loop in a circuit equals zero.