Electronics: Basic Electrical Concepts

• Course name is Electronics
• This course has 3 credits
• The course instructor is Dr. Ahmed Abdelreheem
• The grade distribution method is as follows:
  • Assignments constitute 5% of the grade
  • Quizzes are 20%
  • Tutorial and lab attendance is 5%
  • The Mid-Term Exam is 20%
  • The Final Exam is 50%

Chapter 1: Electricity

• The first chapter covers the following topics:
  • Basic Concepts
  • The Volt, Unit of Potential Difference
  • Charge in Motion Is Current
  • Resistance & Conductance
  • The Closed Circuit
  • The difference between Voltage & Current

Basic Electrical Concepts

• Solids, liquids, and gases contain electrons (negative charge) and protons (positive charge)
• The Bohr atom helps visualize atomic structure
• The nucleus is positively charged and has protons and neutrons.
• Electrons are negatively charged and located in discrete shells.
• The atomic number is the number of protons.
• In a neutral atom, the number of electrons equals the number of protons

Atoms

• Atoms are the smallest particle of basic elements that form physical substances like solids, liquids and gases
• A combination of electrons and protons makes one atom

Atom Composition

• Consists of a central mass called the nucleus
• It has one or more electrons outside the nucleus
• A proton is approximately 1840 times heavier than an electron
• Charge is an electrical property of atomic particles and is measured in coulombs (C)
• The charge on one electron is negative and equals 1.602 x 10^-19 C, which is referred to as electronic charge

Electric Charge Flow

• A unique feature of electric charge or electricity is that it is mobile
• Electric charge can be transferred from one place to another
• The mobile charge moves to where it can be converted to another form of energy
• When a conducting wire is connected to a battery, charges are compelled to move
• Positive charges move in one direction, negatives move in the opposite direction

Electric Current

• A collective movement of charges creates electric current
• Electric current is the time rate of change of charge, measured in amperes (A)
• Formula: i = dq/dt, where i is current, q is charge, and t is time
• 1 ampere = 1 coulomb per second
• Direct Current (DC) is a current that remains constant
• Alternating Current (AC) is a current that varies sinusoidally with time

The Volt Unit of Potential Difference

• Potential refers to the possibility of doing work
• Charge has the potential to do the work of moving another charge either by attraction or repulsion
• Unlike charges have a difference of potential
• The potential difference between two points creates one volt when one joule of energy is expended in moving one coulomb of charge between those points
• V (voltage) = W (work in joules) / Q (charge in coulombs)
• Constant voltage can be called DC voltage and can be represented by V
• A sinusoidally time-varying voltage is called AC voltage and is represented by v
• DC voltage is produced by a battery
• AC voltage is produced by an electric generator
• Work has to be done in separating electrons and protons in order for charge to occur, resulting in stress and strain in the charges
• The force between the charges is in the electrical field

Electric Current Production

• Charge must be moved by a difference in potential to produce current
• Free electrons are charges that can be forced to move relatively easily by a potential difference
• A current flow is a drift of electrons moving from a point of negative charge to a point of positive charge

Ampere of Current

• Unit for stating the amount of current, defined in rate of flow of charge
• When 6.25 x 10^18 electrons flow past a given point per second, the current is one ampere (A)
• 1 Ampere is 1 Coulomb of charge per second
• The ampere unit is named after André M. Ampère (1775–1836)
• Formula to calculate current based on charge is I = Q/T

Current Direction

• Moving charges that provide current have negative polarity such as the free electrons of copper atoms in metal conductors -Motion between terminals for electrical current is toward the more positive end.
• Common applications for electrical current include:
  • Liquids
  • Gases
  • Semiconductors
• The direction of a resulting current is opposite from the direction of electron flow if positive charges are in motion.

Resistance & Conductance

• Opposition that limits the amount of current that can be produced by the applied voltage is called resistance
• Conductors have very little resistance and insulators offer a large amount of resistance
• Atoms of a copper wire have a large number of free electrons moved easily by a potential difference, resulting in low resistance
• The unit of resistance is the ohm
• One ohm is the resistance that develops 0.24 calorie of heat when one ampere of current flows through it for one second

The Ohm

• Its symbol is R
• Its abbreviation is the Greek letter omega (Ω)
• Resistance is indicated by a zigzag line in diagrams
• Resistors have color codes indicating the resistance value
• The opposite of resistance is conductance
• Its symbol is G and the measurement unit type is siemens (S)

Conductance

• The lower the resistance, the higher the conductance
• An old unit name for conductance is mho (ohm spelled backward)
• G is the reciprocal of R, or G = 1/R

Closed Circuits

• Any electric circuit has these characteristics:
  • A source of potential difference
  • Apply a voltage
  • There must be a complete path for current flow
  • The current path has resistance

Voltage and Current

• Current moves through the circuit; the applied potential differences do not
• Electrons flow from one side to the other, while the current is flowing around the circuit
• The potential difference remains across the filament and does the work of moving electrons through resistance

Potential Difference (PD)

• It has to be measured across two points.
• If a circuit is opened by disconnecting the bulb, no current can flow
• The battery has its potential difference
• A voltmeter placed across terminals will read 1.5V even with no electrical flow
• Voltage exists without current, but current cannot exist without voltage

Direct Current (DC) and Alternating Current (AC)

• Current flows in a circuit, electrons leave the negative terminal and the same number of conductors are returned to the positive terminal
• Chemical action separates electrons and protons to maintain negative and positive charges that provide potential difference
• The battery keeps the current flowing
• Circuits carries energy of a voltage source current through the filament of a bulb to enable heat energy
• A battery is the source of a circuit for its voltage output for potential to be used
• The term "load" means the load current unless otherwise specified

Open and Short Circuits

• A circuit with any open or broken path is an incomplete circuit
• The open circuit can exist in the connecting wires
• The resistance of an open circuit is considered infinitely high and the circuit has no electrical flow

Short Circuits

• Cases involve a closed path across terminals but resistance is practically zero.
• Results in too much electrical flow and results in a short circuit
• The energy will bypass the load resistance

Electron flow versus Conventional Current

• Conventional flows in the opposite direction from electrical current
• Conventional current flow generally describes analyzing circuits, and is rooted traditional physics definitions
• Conventional electrical flow is motion from positive value to negative

Voltmeters

• Used to measure Voltage or Potential Difference

Chapter 3: Ohm's Law

• This chapter will cover: -Ohm's Law -Electric Power -Power Dissipation in Resistance -Power Formulas

Ohm's Law Facts

• Discovered in 1826 by Georg Simon Ohm
• Mathematical relationship between voltage, current, and resistance
• Basis of all circuit analysis in electronics
• Amount of current is directly proportional to the voltage
• Amount of current is inversely proportional to the resistance
• Ohm's law is stated as I = V/R
• High voltage circuits have small current values

Increasing Current

• Applying additional voltage increases the electrical flow to light a bulb with more intensity
• Applying a low value of voltage in a very low resistance circuit produces large volumes of current
• Ohm's law formulas are: -I = V/R -V = I * R -R = V/I

Definitions

• One ampere equals one volt per ohm.
• One volt equals one ampere times one ohm.
• One Ohm equals 1 volt divided by 1 amp.

Conversion Guide

• Volts across kilohms produce milliamperes of current
• Volts across megohms produces microamperes

Electricity

• The three forms of Ohm's law: -Current -Potential difference -Resistance

Electric Power

• Electric power unit of is the watt (W), after James Watt (1736–1819)
• One Watt is performed work of one second by one volt
• Power is volts times amperes, or P=VXI To find the power formula, several equations can be done, including I =P/V or V=P/I

Power and Output

• Power formula rearrange to get I, P, or V depending what needs to be solved for
• P = V x I = IR x I = I^2 / R, This results in the heat in a resistance
• P = V^2/R formula is also used with the power produced by the electrical flow in the resistance.

Power Formulas Used to Solve Problems

• P = VI or I = P/V or PV = P/I
• P = I^2 or R= P/I^2 or I = SqRt( P/R )
• P = V^2/R of is R= V^2/P or V=( PR )*SqRt

Introduction to basic electrical concepts, including charge, atomic structure (electrons, protons, neutrons, nucleus), and atomic number. Covers fundamental concepts relevant to the field of electronics. Explains the concept of charge in motion.