Ligjërata I, Bazat e Inxhinierisë Elektrike dhe Elektronike

Page 1: Introduction

  • UNIVERSITETI PËR BIZNES DHE TEKNOLOGJI - UBT

  • FAKULTETI: Fakulteti i Shkencave Kompjuterike dhe Inxhinierisë (Bachelor) 2024-2025

  • Kursus: Bazat e Inxhinierisë Elektrike dhe Elektronike

  • Viti i parë: (Semestri i parë)

  • Ligjërata e parë: Prof.Kjani Guri, PhD Candidate

Page 2: Introduction to Electrical and Electronic Engineering

1.1 What are Units

  • The International System of Units (SI) is fundamental for all measurements.

  • Comprised of 7 base units, which lead to all other derived units, called derived units.

Base Quantities and Units

Quantity

Unit

Symbol

Mass

Kilogram

kg

Length

Meter

m

Time

Second

s

Electric Current

Ampere

A

Temperature

Kelvin

K

Luminous Intensity

Candela

cd

Amount of Substance

Mole

mol

Page 3: Derived Quantities

Derived Units

Quantity

Unit

Symbol

Force

Newton

N

Power

Watt

W

Energy

Joule

J

Resistance

Ohm

Ω

1.1.1 Standard Form

  • Standard form is a method for writing large and small numbers compactly, e.g. 300,000,000 m/s = 3 x 10^8 m/s

Page 4: Graphs

  • Practice plotting the dependent variable along the vertical axis and the independent variable along the horizontal axis.

  • E.g. In a graph of distance traveled vs time elapsed, distance is the dependent variable, as it depends on time.

Multiplying Factor Prefixes

Factor Type

Prefix

Symbol

10^12

Tera

T

10^9

Giga

G

10^6

Mega

M

10^3

Kilo

k

10^-3

Milli

m

10^-6

Micro

μ

10^-9

Nano

n

10^-12

Pico

p

Page 5: Example of Graph Interpretation

  • The graph depicts the distance traveled over time, showing a journey of 30 km in the first 3 hours and an additional 10 km in the next 2 hours with no further distance traveled (vehicle stationary).

  • Since distance is divided by time taken, it reflects the vehicle's speed at any point in time.

Page 6: Slope Interpretation

  • When δs = 0, the speed must also be zero (v = 0).

  • A nonlinear graph illustrates the displacement of a mass subjected to simple harmonic motion, known as a sine wave.

  • The slope gives velocity at each moment, steepest when crossing zero displacement (maximum speed) and zero at the peaks (zero speed).

Page 7: Basic Electrical Concepts

1.2 Basic Concepts

  • Matter is composed of atoms; the simplest model is Bohr's model.

  • Atoms consist of a central nucleus with protons and neutrons, surrounded by electrons in different orbits.

  • Neutrons are often ignored in electrical concepts as they do not contribute directly to electrical behavior.

Page 8: Understanding Electric Charge

  • This model helps explain electrical energy and how devices work.

  • Protons have a relatively large mass but do not actively participate in electrical flow; it's the electrons' behavior that is key.

  • Both protons and electrons have electric charge, measured in Coulombs (C), where charge is denoted as Q.

  • An atom is electrically neutral, possessing equal numbers of electrons and protons.

Page 9: Material Classification

  • Materials are classified as conductors, insulators, or semiconductors based on the number of "free" electrons available.

  • Conductors have many free electrons, moving randomly, while insulators have very few or none.

  • Semiconductors fall between these two categories.

  • Strong communication skills are essential for engineers to effectively convey ideas.

Page 10: Electric Current

1.2.1 Electric Current

  • Electric current is the speed of free electrons moving in one direction through a material.

  • Charge is measured in Coulombs and time in seconds, leading to current having units of Coulombs/second (Ampere).

  • The relationship between charge (Q), current (I), and time (t) is given by:

    Q = It

Page 11: Electromotive Force (emf)

1.2.2 Electromotive Force (emf)

  • Random electron motion does not constitute electric current without a net flow in a defined direction.

  • To direct free electrons, an electromotive force (emf) must be applied.

  • Symbol: E, Unit: Volt (V).

  • Typical emf sources include cells, batteries, and generators, and the current flowing is directly proportional to the emf applied.

Page 12: Electric Resistance

1.2.3 Resistance

  • The resistance of a circuit material influences the amount of electric current that flows.

  • Resistance is measured in Ohms (Ω).

  • Conductors have low resistance due to available free electrons, while insulators have high resistance.

  • Pure semiconductors typically behave like insulators, but impurities can enhance conductivity.

Page 13: Potential Difference

1.2.4 Potential Difference

  • When current flows through resistance, a potential difference occurs.

  • Measured in volts, potential difference signifies voltage levels between two points in a circuit; however, emf and potential difference are not the same.

  • Emf causes current flow, while potential difference results from that flow through resistance.

Page 14: Electrical Circuit

  • The equivalent electric circuit comprises a battery, conductors, and resistors to limit current flow.

  • The total of potential differences (V1 and V2) equals the total emf in volts: E = V1 + V2.

Page 15: Conventional Current vs Electron Flow

1.2.5 Conventional Current and Electron Flow

  • The direction of conventional current flows from battery's positive to negative terminals.

  • Since electrons are negatively charged, their flow moves in the opposite direction.

  • The convention is used for most practical circuit analysis, while electron flow is referenced for explaining effects in semiconductor devices.

Page 16: Ohm's Law

1.2.6 Ohm's Law

  • Ohm's Law states that the potential difference across a resistor is proportional to the current flowing through it when other conditions remain constant.

  • Mathematical representation: V = IR.

Page 17: Internal Resistance

1.2.7 Internal Resistance (r)

  • Real power sources possess internal resistance, e.g. a typical 12 V battery consists of charged plates connected via an electrolyte.

  • The internal resistance limits the current flowing when a circuit is closed.

  • Ideal sources can be assumed to have zero internal resistance for calculation purposes.

Page 18: Energy

1.2.8 Energy

  • Energy is a system's capacity to perform work.

  • Work corresponds to energy transfer from one system to another.

  • Electrical current generates heat, exemplified by electric heaters.

  • Joule's findings correlate heat production with the square of current and the time duration flowing: W = I²Rt.

Page 19: Power

1.2.9 Power

  • Power (P) signifies the rate at which work is done or energy is transferred.

  • Defined unit: Watt (W).

  • Power can be expressed as:P = W/t, P = VI, P = I²R, P = V²/R.

Page 20: Commercial Energy Units

1.2.10 Energy Commercial Unit (kWh)

  • Joules serve as SI unit but are impractical for large energy consumption.

  • Household energy consumption is typically measured in kilowatt-hours (kWh).

  • Example: a 3 kW heater running for 12 hours consumes 36 kWh of energy.

Page 21: AC and DC Measurements

1.2.11 AC and DC Measurements

  • Previously covered emf and current are DC magnitudes.

  • Common electrical supply from the grid is Alternating Current (AC) where current periodically reverses direction.

  • AC supply is typically sinusoidal, while DC flows in only one direction.

Page 22: Factors Influencing Resistance

1.2.12 Factors Affecting Resistance

  • Resistance of a material depends on:I. LengthII. Cross-sectional areaIII. Material typeIV. Temperature

  • Resistance formula: R = ρ(l/S), where ρ is resistivity.

Page 23: Temperature Effect on Resistance

  • Resistance changes with temperature, with pure conductors showing higher resistance at elevated temperatures and thus having a positive temperature coefficient.

  • Conversely, carbon and semiconductors show reduced resistance with temperature increases, possessing a negative temperature coefficient.

Page 24: Temperature Resistance Coefficient

  • The temperature resistance coefficient is defined by the ratio of resistance change per temperature change to the resistance at a given temperature.

  • Symbol: α; unit: per degree Celsius /°C.

  • Resistance can be recalculated at different temperatures with: R1 = R0(1 + αθ1).

Page 25: Measuring Instruments

1.2.13 Use of Measuring Instruments

  • Measuring electrical quantities is essential in engineering; proficiency with measurement instruments like ammeters and voltmeters is crucial.

Page 26: Ammeters and Voltmeters

  • Ammeter: Measures current; must be connected in series with the circuit to measure current flowing through it.

  • Voltmeter: Measures voltage; connected across two points in a circuit, akin to a simpler use procedure than an ammeter.

Page 27: Multimeters

  • Multimeter: Combination of ammeter, voltmeter, and ohmmeter in one device, available in analog or digital forms.

  • Digital multimeters display readings on numeric screens for easier interpretation.

Page 28: Handling Measurement Instruments

  • Measurement instruments are fragile and need careful handling to avoid damage.

  • Guidelines for handling them include:

    1. Ensure power supply is off during connections.

    2. Start with high ranges before selecting lower ones for better accuracy.

    3. For series readings, aim for a range accommodating entire series.

    4. Turn off and disconnect the power supply after use.

Page 29: Summary of Key Equations

  • Charge: Q = It (Coulomb)

  • Ohm's Law: V = IR (Volt)

  • Terminal p.d.: V = E - Ir (Volt)

  • Energy: W = VIt = 12Rt (Joule)

  • Power: P = W/t = VI = I²R = V²/R (Watt)

  • Resistance: R = ρ(l/S) (Ohm)

  • Resistance at specified temp.: R1 = R0(1 + α) (Ohm)