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Linear Circuits

An introduction to electric circuit elements and a study of circuits containing such devices.

Dr. Bonnie H. FerriProfessor and Associate ChairSchool of Electrical and Computer Engineering

School of Electrical and Computer Engineering

Concept Map: Background Module 1

3

Resistive

Circuits

Reactive

CircuitsFrequency

Analysis

Power

BackgroundBackground

Background• Charge

• Current

• Voltage

• Power

• Resistor

• Sources

• Circuits

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Nathan V. ParrishPhD Candidate & Graduate Research AssistantSchool of Electrical and Computer Engineering

School of Electrical and Computer Engineering2

Charge and

Current

•Calculate the force charges exert on one another•Calculate functions of charge and current

� Calculate the forces two point charges exert on each other

� Calculate current based on a charge function� Calculate charge based on a current function

Lesson Objectives

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� Property of matter� Quantized� Measured in Coulombs ( C )

Electric Charge

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Electromagnetic Force

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Electric Fields

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Electrical Current

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Reference Directions

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� Discussed charge as a property of matter� Calculated forces of charge using Coulomb’s Law� Explored electric fields – the means of this

interaction� Described current as the time derivative of charge� Emphasized the importance of current reference

directions

Summary

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1/5/2014

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Nathan V. ParrishPhD Candidate & Graduate Research AssistantSchool of Electrical and Computer Engineering

School of Electrical and Computer Engineering2

Voltage

•Modify voltage values to reflect voltage references•Describe how a chemical battery works•Identify if a battery is charging or discharging

� Calculate voltage from the energy gained/consumed as a charge moves through an electric field

� Correctly specify voltages as references change� Describe the operation of a chemical battery� Identify if a battery is charging or discharging

based on the voltage reference and current flow

Lesson Objectives

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Voltage

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Origin of Voltage

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Voltage Reference

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Example: Finding Voltages

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Lead-Acid Batteries - Discharging

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Cathode Anode

Lead-Acid Batteries - Charging

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Anode Cathode

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� Charge crates electric fields� Voltage is energy gained/released as charges

move through an electric field� Described how voltage originates from

differences in charge density� Case study: how lead-acid batteries work

Summary

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1/5/2014

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Nathan V. ParrishPhD Candidate & Graduate Research AssistantSchool of Electrical and Computer Engineering

School of Electrical and Computer Engineering2

Power and Energy

•Calculate power and energy•Describe the difference between power and energy•Use conservation of energy to find unknown energy•Use power to calculate current or voltage

� Calculate power from energy function� Calculate energy from a power function� Use conservation of energy to find power of an

unknown device� Calculate power from voltage and current� Find a voltage or a current for a device with a

known power

Lesson Objectives

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Power

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Instantaneous Change

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You run a power company. Do you charge customers for power or energy? Why?

Charging for Power

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Pause

Conservation of Energy

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Reference Direction

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Using Power for Analysis

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Pause

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� Described the relationship between power and energy and how to calculate them

� Described how voltage and current relate to power

� Presented a derivation for conservation of power and how this property is used in analysis

� Solved first simple analysis problem

Summary

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1/5/2014

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Nathan V. ParrishPhD Candidate & Graduate Research AssistantSchool of Electrical and Computer Engineering

School of Electrical and Computer Engineering2

Introduction to

Circuit Diagrams

•Identify a collection of basic circuit elements•Be able to identify nodes•Identify short/open circuits•Identify equivalent circuit diagrams

� Identify a set of circuit elements� Identify the nodes in a circuit diagram� Recognize self-contradictory circuits� Identify open/closed circuit� Identify when two circuits are equivalent� Modify a circuit to form an equivalent circuit

Lesson Objectives

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Circuit Diagrams

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� Devices are presented with some known parameters

� We wish to identify the behavior of the device

� Identify behavior based on the circuit using calculation

What is Circuit Analysis?

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� Zero internal resistance� Nodes and junctions� Zero voltage drop on node

� Arbitrary current possible

Wires

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Independent Sources

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Independent Voltage

Source

Independent Current

Source

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Dependent Sources

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Dependent Voltage

Source

Dependent Current

Source

Resistors

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� Devices for resisting current� Drawn as zig-zag lines� Number of zigs ands zags can vary� Other similar devices will be

introduced as they are encountered

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Ground

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� Common Point of reference� Path of electrons

� Lightning rod (literal ground)� Prevent electrocution� Prevent damage to sensitive

components

Open/Short Circuits

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Self-Contradictory Circuits

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Putting It Together

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Changing Circuits

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� Described the concept of a node and how to identify one� Introduced independent and dependent voltage and current

sources� Introduced a resistor – a device that will be discussed in

more detail later� Presented the idea of a ground� Showed examples of self-contradictory circuits� Described how circuits can be equivalent

Summary

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Dr. Bonnie H. FerriProfessor and Associate ChairSchool of Electrical and Computer Engineering

School of Electrical and Computer Engineering

Module 1

Background

Wrap Up

Summary of Background Module

Concept Map: Background Module 1

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Resistive

Circuits

Reactive

CircuitsFrequency

Analysis

Power

BackgroundBackground

Background• Charge

• Current

• Voltage

• Power

• Resistor

• Sources

• Circuits

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� Understand charge and current� Be able to calculate the effect of one charge on

other charges

� Be able to calculate current from charge flow in time

Important Concepts and Skills

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� Understand how voltage is created by differences in charge density

� Understand how chemical reactions can cause a voltage

� Be able to use voltage references

� Be able to identify some basic circuit elements� Be able to identify nodes of a circuit diagram

� Be able to identify open/short circuits

� Be able to move elements of a diagram

Important Concepts and Skills

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� Be Able to calculate power from energy� Be able to analyze circuit using conservation of power

� Be able to analyze circuit using power, voltage, and current