Lecture7

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

CS 21 - Computer Organization and Assembly Language Programming Lecture 7 Introduction to Electrical Devices and Circuits University of the Philippines - Diliman College of Engineering Department of Computer Science

What is Electricity?

Fundamental Quantities

Ohm’s Law

Outline

1

What is Electricity?

2

Fundamental Quantities

3

Ohm’s Law

4

Series and Parallel Interconnection

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Ohm’s Law

Outline

1

What is Electricity?

2

Fundamental Quantities

3

Ohm’s Law

4

Series and Parallel Interconnection

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Ohm’s Law

Electricity Defined

Electricity has two common meanings: (1) Energy that causes ”things” to turn on (2) Flowing motion of electric charges

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Electricity Defined

Electricity has two common meanings: (1) Energy that causes ”things” to turn on (2) Flowing motion of electric charges

Trivia: Dagitab is the Filipino term for electricity

What is Electricity?

Fundamental Quantities

Ohm’s Law

Outline

1

What is Electricity?

2

Fundamental Quantities

3

Ohm’s Law

4

Series and Parallel Interconnection

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Ohm’s Law

Fundamental Electrical Quantities

Charge Current Voltage Resistance Power

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Charge

Basic physics: two types of charges - positive and negative

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Charge

Basic physics: two types of charges - positive and negative Positive: protons Negative: electrons

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Charge

Basic physics: two types of charges - positive and negative Positive: protons Negative: electrons In this class: only electron flow is relevant

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Charge

Basic physics: two types of charges - positive and negative Positive: protons Negative: electrons In this class: only electron flow is relevant Unit of measurement: Coulombs (C)

What is Electricity?

Fundamental Quantities

Ohm’s Law

Current Flow of charges or ”charges in motion”

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Ohm’s Law

Current Flow of charges or ”charges in motion” ”Kuryente”

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Current Flow of charges or ”charges in motion” ”Kuryente”

Unit of measurement: Amperes (A) 1A = 1C/s how many charged particles pass through per second

What is Electricity?

Fundamental Quantities

Ohm’s Law

Voltage

Energy required to ”push charges”

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Ohm’s Law

Voltage

Energy required to ”push charges” Also known as potential difference

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Ohm’s Law

Voltage

Energy required to ”push charges” Also known as potential difference Unit of measurement: Volts (V) 1V = 1J/C how much energy is spent to push an electron

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Resistance

Opposition to the current

Ohm’s Law

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Resistance

Opposition to the current ”Degree of hardship”

Ohm’s Law

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Resistance

Opposition to the current ”Degree of hardship” Unit of measurement: Ohms (Ω) 1Ω = 1V/A remember, resistance is inversely proportional to current

What is Electricity?

Fundamental Quantities

Ohm’s Law

Power

Rate at which energy is expended

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Ohm’s Law

Power

Rate at which energy is expended Unit of measurement: Watts (W) 1W = 1VA energy in terms of V, rate in terms of A

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Ohm’s Law

Power

Rate at which energy is expended Unit of measurement: Watts (W) 1W = 1VA energy in terms of V, rate in terms of A 1W = 1VA = 1 (J/C) (C/s)

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Ohm’s Law

Power

Rate at which energy is expended Unit of measurement: Watts (W) 1W = 1VA energy in terms of V, rate in terms of A 1W = 1VA = 1 (J/C) (C/s) 1W = 1VA = 1 (J/s)

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Types of Circuits and Circuit Elements

Circuit elements can be classified according to the relationship of the current through the element to the voltage across the element.

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Types of Circuits and Circuit Elements

Circuit elements can be classified according to the relationship of the current through the element to the voltage across the element.

Resistor - voltage across is directly proportional to the current

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Types of Circuits and Circuit Elements

Circuit elements can be classified according to the relationship of the current through the element to the voltage across the element.

Resistor - voltage across is directly proportional to the current Independent sources - voltage is completely independent of current, and vice versa

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Types of Circuits and Circuit Elements

Circuit elements can be classified according to the relationship of the current through the element to the voltage across the element.

Resistor - voltage across is directly proportional to the current Independent sources - voltage is completely independent of current, and vice versa Dependent or controlled sources - source voltage or current depends upon a current or voltage elsewhere

What is Electricity?

Symbols

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Convention

In volt source (battery symbol), the longer leg is positive

What is Electricity?

Fundamental Quantities

Ohm’s Law

Convention

Current flows from the positive side

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Convention

The receiving side of any passive element is positive

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Convention

Note: each element should have the plus-minus pair

What is Electricity?

Fundamental Quantities

Ohm’s Law

Outline

1

What is Electricity?

2

Fundamental Quantities

3

Ohm’s Law

4

Series and Parallel Interconnection

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Important Concept The flow of current always encounters some resistance, resulting in a voltage drop and the conversion of electric energy to heat.

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Ohm’s Law

Ohm’s Law shows the relationship between current, voltage and resistance in an electrical network V=IR Where V = voltage I = current R = resistance

What is Electricity?

Fundamental Quantities

Ohm’s Law

Outline

1

What is Electricity?

2

Fundamental Quantities

3

Ohm’s Law

4

Series and Parallel Interconnection

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Series Connection

series - one node of an element is a connected to a node of another

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Parallel Connection

parallel - two or more elements share the same nodes

What is Electricity?

Fundamental Quantities

Resistor Equivalences

Ohm’s Law

Series and Parallel Interconnection

What is Electricity?

Example 1

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

What is Electricity?

Example 2

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Example 3 What is the equivalent resistance value of this network?

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Things to remember

Elements in series have the same current running through them Elements in parallel have the same voltage across them

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Things to remember

Elements in series have the same current running through them Elements in parallel have the same voltage across them Wires have zero resistance (for simplicity)

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

Things to remember

Elements in series have the same current running through them Elements in parallel have the same voltage across them Wires have zero resistance (for simplicity) Follow the voltage-current convention

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

More Examples

Find the resistance of the equivalent resistor.

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

More Examples

Find the resistance of the equivalent resistor.

What is Electricity?

Fundamental Quantities

Ohm’s Law

Series and Parallel Interconnection

More Examples

Find the resistance of the equivalent resistor.

What is Electricity?

Fundamental Quantities

Ohm’s Law

So...

Any questions?

Series and Parallel Interconnection