Introduction to Circuit Theory and SI Units

Instructor: Dr. Muhammad

Course Outline

• Exams: Two term exams and a final exam
• Assignments: Four assignments
• Topics: Circuit theory basics, Ohm's law, Kirchhoff's law, analytical theorems, electronics foundations, diodes, transistors, basics of computers (hardware and software), SI units

SI Units (International System of Units)

• Fundamental for analyzing hardware circuits
• Basic Units: meter, kilogram, second, Kelvin, ampere, mole, Candela
  • Length (m): Meter (m)
  • Mass (kg): Kilogram (kg)
  • Time (s): Second (s)
  • Electric current (A): Ampere (A)
  • Temperature (K): Kelvin (K)
  • Amount of substance (mol): Mole (mol)
  • Luminous intensity (cd): Candela (cd)

Fundamental Definitions and Modern Interpretations

• Meter: Distance light travels in vacuum in 1/299,792,458 of a second
• Second: Duration of 9,192,631,770 cycles of radiation of cesium-133 atom
• Kilogram: Mass of a platinum-iridium cylinder stored in Paris
• Kelvin: 1/273.16 of the thermodynamic temperature of water's triple point
• Ampere: Current that generates a force of 2 x 10^-7 N/m between two parallel wires 1 meter apart
• Candela: Luminous intensity of 1/600,000 m² cavity at freezing platinum's temperature
• Mole: Amount of substance in 0.012 kg of carbon-12

Derived Units

• Joule (J): Energy to move 1 kg 1 m
• Watt (W): 1 joule per second; derived unit for power
• Coulomb (C): Unit of electric charge; 6.25 x 10^18 electrons or protons

Decimal System Prefixes

• Negative Powers:
  • Yocto (y): 10^-24
  • Zepto (z): 10^-21
  • Atto (a): 10^-18
  • Femto (f): 10^-15
  • Pico (p): 10^-12
  • Nano (n): 10^-9
  • Micro (μ): 10^-6
  • Milli (m): 10^-3
  • Centi (c): 10^-2
  • Deci (d): 10^-1
• Positive Powers:
  • Yotta (Y): 10^24
  • Zetta (Z): 10^21
  • Exa (E): 10^18
  • Peta (P): 10^15
  • Tera (T): 10^12
  • Giga (G): 10^9
  • Mega (M): 10^6
  • Kilo (k): 10^3
  • Hecto (h): 10^2
  • Deca (da): 10^1

Atomic and Electronic Structure

• Atom: Building block of all materials, consists of electrons, protons, neutrons
• Electrons: Negatively charged particles
• Protons: Positively charged particles
• Neutrons: Neutral particles
• Atomic Stability: Number of electrons = number of protons in a neutral atom
• Valence Electrons: Electrons in the outermost shell, important for conductivity
• Hydrogen Example: Simplest atom, one proton, one electron
• Carbon and Copper Atoms: Carbon with 6 protons/electrons, Copper with 29 protons/electrons

Conductors, Insulators, and Semiconductors

• Conductors: Allow easy flow of electrons (e.g., copper, silver)
• Insulators: Do not allow easy flow of electrons, store electricity better (e.g., rubber, glass)
• Semiconductors: Materials that can act as both under different conditions (e.g., silicon, germanium)
  • Carbon as Semiconductor: Conducts less than metals but more than insulators
  • Free Electrons: Cause electrical conductivity

Coulomb's Law and Electrostatics

• Coulomb (C): Unit of electric charge
• Static Electricity: Charge accumulation without current flow
• Coulomb's Constant: Force between two charges
• Polarity:
  • Negative: Rubber, resinous materials
  • Positive: Glass, other materials

Problem-Solving Strategy

1. Read the problem statement slowly and carefully
2. Identify the goal of the problem
3. Collect the known information
4. Decide the appropriate technique
5. Construct an appropriate set of equations
6. Solve the equations
7. Check if additional information is required
8. Attempt a solution
9. Verify if the solution is reasonable or expected

Sample Exercises

1. Atomic number of atom with 29 electrons?
2. Interaction of charges with 1 Coulomb each?
3. Electronic distribution of atom with atomic number 23?

Future Topics

• Resistors, capacitors, inductors, Ohm's law

This concludes Lecture 1. Next lecture: Properties and analysis of resistors, capacitors, inductors, and Ohm's law.