ECE 2020

Atom is made of

nucleus and electrons

Nucleus contains

protons and neutrons

Protons are

positively charged

Electrons are

negatively charged

An electron carries what charge

-1.602x10^(-19)

What can we change about an atom?

only the number of electrons

Law of Conservation of Electric Charge

Charge cannot be created or destroyed, it can only transfer

What has to be true about an atom for it to be negatively charged?

it has to have more electrons than protons

Electric Current

movement of electric charge in a wire over a period of time

Variable for current

i

Current is measured in

amps = Columb's/second

Current flows from what to what?

Higher potential to lower potential

Electron drift goes from what to what?

lower potential to higher potential

Voltage

energy required per unit charge required to move that charge between 2 points

Voltage is measured in what?

Volts = Joule/Columb

Passive Element

electrical component that does not generate power, but dissipates, stores, and/or releases it

Ideal Wire

Conducts charge without loss of potential

Objective of Circuit Analysis

Determine unknown currents and voltages

Branch

single electrical pathway, once you have options, branch is over

Node

Junction of 2 or more branches, charge can flow without crossing a component

Node voltage is always relative to what

the reference node chosen

Components in Series

MUST be on the same branch, share the same current

Components in Parallel

Sharing same nodes on both sides, have the same voltage

To find elements in Parallel

Color each node differently
Any 2 elements that have the same 2 colors on each side are in Parallel, they can be chained

Loop

Any closed pathway, required for current to flow

Mesh

A loop that does not contain other loops

Smallest quantity of charge

electron or proton

Unit for charge

Coulomb

Variable for charge

q

Electron Drift

The process of sequential migration of electrons from one atom to the next.

Ohm's law

Current (i) entering + teminal of voltage v across a resistor is given by

i=v/R

Ideal, independent voltage source

provides specified voltage across terminals regardless of load or circuit

Ideal, independent current source

provides specified current flowing through it, regardless of voltage connected to it

Passive sign convention

Direction of current is into +v terminal of device
(Current must flow from higher to lower potential)

Resistive Circuit

containing only sources and resistors

Conductivity

measure of how easily electrons drift through material when external voltage is applied across it

Resistivity

inverse of conductivity

Ohm's Law

V=iR

(voltage = current * resistance)
ONLY true across a resistor

Ideal Linear Resistor:

One whose resistance is constant and independent of current

Circuit topology

study of geometrical properties of electrical circuits

Kirchoff's Current Law

Algebraic sum of currents entering a node must be zero

Kirchoff's Voltage Law

Algebraic sum of voltages around a closed loop must be zero

Power

Amount of work per unit of time

Power = voltage * current

P=vi

What is the voltage at the ground

0 volts

If power across a component is positive,

then power is dissipated or consumed

If power across a component is negative,

then power is generated or supplied

What do we know about power across a resistor?

it is always positive

Law of conservation of power

the sum of the power in a system is zero

When is Ohm's law true?

ONLY across a resistor

Power across a resistor =

P=v^2/R

Voltage Division

Only applies on resistors in series
User KVL at mesh