Chapter 1-1 SI Units Voltage and Current basic circuit elements passive sign convention.

What this course is about 1.Finding unknown Voltages and Currents 2.Finding energy delivered or used 3.Finding component values/configurations to create desired voltages and currents A.Learn fundamental definitions, rules and techniques B.Practice, practice…..and more practice

Problem Solving Approach 1.Identify what’s given and what’s to be found 2.Sketch a circuit diagram and/or modify existing diagram 3.Decide on method or approach 4.Solve it (may need to go back) 5.Check to see if solution make sense!!!!!!

SI Units

Electrical Charge To characterize electrical charge behavior we must start at the atom which consist of 1.Proton(s):? charges 2.Neutron(s):? charges 3.Electron(s): ? charges Charge properties 1.Like charges _______ one another 2.Unlike charges ______ one another 3.The force of repulsion or attraction obeys the inverse square law

A atom that has the same number of positive particles (protons) and negative particles (electrons) has a net _________ charge.

If an atom loses an electron, it has a net _________ charge

Once an electron is removed from an atom, which requires some form of work, we are left with a positively charged atom and a free, negatively charged, electron The free electron may 1.Be captured by a nearby positive atom 2.Remain free and migrate to the surface of the material which occurs because _____________? A bunch of charge stationary at the surface is ________ electricity

Electric Voltage

When we discuss or measure an electrical voltage we are looking at the potential difference between two points

Electric Current

When we discuss or measure an electrical current we are looking at the charge flow through an element

Will all materials support a current, allow charge to flow?

Band Theory

Ideal Basic Circuit Element 1.Has only two terminals 2.Can be described mathematically in terms of current and/or voltage. 3.Cannot be subdivided into other elements.

Passive Sign convention: Whenever the reference direction for the current in an element is in the direction of the reference voltage drop across the element, use a positive sign in expressions relating the voltage to the current. Otherwise use a negative For circuit analysis we must assign a reference polarity for voltage and reference direction for current We will adopt the passive sign convention for this class

Examples of passive sign convention

Examples of passive sign convention (Resistor)

What you should know 10 Future Technologies That May Change The World 1.SI Units related to Electrical Circuits 2.Definitions Voltage and Current 3.Definition of basic circuit element 4.Be able to apply the passive sign convention