ENG1300 Lecture 1: Introduction to DC Circuits and Course Overview

Course Introduction to ENG1300

• Overview of ENG1300

  • This course serves as a fundamental introduction to electrical engineering and circuit analysis.
  • The primary objective is to learn how to solve circuits from an engineering perspective, which involves determining operating conditions such as node voltages and branch currents.
  • The course covers both DC (Direct Current) circuits and AC (Alternating Current) circuits.

• Historical Perspective and Instructor Background

  • YS Kushar (Senior Lecturer and Course Coordinator):
    • Started university journey 25 years ago in 2001; his first lecture was also an introduction to DC circuits.
    • Received undergraduate degree in electrical engineering.
    • Moved to Australia in 2007 for a PhD at the Australian National University in Canberra.
    • Worked as a research scientist in Singapore.
    • Joined UQ in 2017 as an industry research fellow and became a Senior Lecturer in 2024.
  • Sasan Ahadi Hazai (Senior Lecturer and Course Coordinator):
    • Received bachelor's degree in 2009 in Iran.
    • Completed a Master's in telecommunications engineering at Istanbul Technical University in Turkey.
    • Moved to Australia for a PhD (2012–2016).
    • Recipient of the Advanced Queensland Research Fellowship.
    • Industry experience in Norway and the United States.
  • Professor Phil Terrill:
    • Acknowledged for developing the course from scratch and teaching it in Semester 1.

• Engineering in Everyday Life

  • Circuit solving is an everyday activity, such as driving a car.
  • Example: Switching on headlights involves a DC source (battery) supplying power to a load (represented as a resistor).
  • Engineering involves looking at these connections to determine voltage at nodes and current through branches.

Course Structure and Enrollment

• Enrollment Mode

  • The course is strictly in-person.
  • Weekly schedule consists of one lecture and two practical sessions.
  • Most assessments are conducted on-campus.

• Practical Sessions (Pracs)

  • Each student attends two sessions per week (P1 and P2).
  • Nomenclature: "Prac 3A" refers to the first practical (P1) of Week 3; "Prac 5B" refers to the second practical (P2) of Week 5.
  • Sign-on occurs via the My Timetable app.
  • Due to high volume (classes of approximately 99 students), switching sessions is difficult and requires contacting the timetable team via email.

• Teaching Team and Support

  • Tutors: A team of 20 tutors assists with practicals.
  • Discussion Boards: Ed Discussion is used for online queries; responses are typically provided within 24 hours (excluding holidays/weekends).
  • First-Year Lecture Theater Tutor: Starting in Week 2, a dedicated tutor will be available for three hours weekly in the first-year lecture theater for walk-in support.

Engineering Professionalism and Ethics

• Student Responsibility

  • Students are expected to transition from a high school mindset to an undergraduate engineering mindset.
  • This involves proactive self-learning and taking responsibility for missed content.
  • Communication must follow professional etiquette; emails to staff should be formal and sent from UQ student accounts.

• Lab Safety Protocols

  • All equipment (DC/AC) is safe and operates at extra-low voltage levels, requiring no special license.
  • Students must follow the Queensland Electrical Safety Act; do not attempt complex electrical work at home without a license.
  • Professional practice in the lab includes:
    • Connecting the source only after the circuit design is complete.
    • Switching off and disconnecting the source before modifying the circuit.
    • Standing away from the circuit during the initial power-on.

• Artificial Intelligence (AI) Policy

  • AI tools can provide solutions instantly, but engineering competency requires understanding the underlying logic.
  • AI use is prohibited for most assessments, including exams.
  • If AI is used in permissible contexts (like quizzes), it must be explicitly acknowledged and cited to maintain academic integrity.

Assessment and Grading

• Assessment Items

  1. Weekly Quizzes (11 total): Conducted online via Blackboard Ultra. No quiz for Week 1 or Week 10. Quizzes include a "practice" version (unlimited attempts) and an "assessed" version (maximum of 3 attempts; highest mark counts). Deadlines are typically Mondays at $10:00\,\text{AM}$.
  2. Mid-term Exam: Held in Week 6, 7, or 8, usually on a Saturday or Sunday.
  3. Practical Exam: Held during Week 11. Students must keep both their P1 and P2 slots free until the specific schedule is released in Week 9.
  4. Final Exam: Closed-book exam.

• The Hurdle Requirement

  • Students must achieve at least $45\%$ in the Final Exam to pass the course.
  • Failure to meet this hurdle results in a maximum grade of 3.

• Study Resources

  • Textbook: Electrical Engineering: Principles and Applications by Hambley (not mandatory but recommended for future reference).
  • Blackboard Ultra: Hosts all lecture slides, practical materials (released Friday before the relevant week), and practice exam questions.

Problem Solving and Intuition

• Intuitive Engineering
  • The course aims to teach students how to solve problems when resources or time are constrained.
  • The Apollo 13 Case Study:
    • An electrical engineer project manager in Houston led a team during the lunar mission emergency.
    • The spaceship was $200,000\,\text{miles}$ from Earth with only $2\,\text{hours}$ of oxygen remaining.
    • The team had to build an oxygen-producing device using only spare resources available on the ship within $1\,\text{hour}$.
    • Successful completion of this task is a prime example of intuitive engineering under constraints.

Fundamental Concepts: DC Circuits

• Definitions

  • Electrical Circuit: A collection of circuit elements connected in a closed path by conductors.
  • Closed Path: Essential for current flow; elements not in the closed path do not impact the circuit analysis.
  • Node: A junction point where two or more circuit elements are connected.
  • Branch: A circuit element that connects two nodes. The number of elements equals the number of branches.

• Ohm's Law

  • Defines the relationship between voltage ($V$), current ($I$), and resistance ($R$).
  • Formula: $V = I \times R$
  • Units: Voltage in Volts ($V$), Current in Amperes ($A$), Resistance in Ohms ($\Omega$​).

• Ideal Independent Voltage Source

  • A theoretical component that maintains a constant voltage across its terminals regardless of the current flowing through the rest of the circuit.

Series and Parallel Resistors

• Series Connection

  • Resistors are connected end-to-end.
  • Characteristics: The same current ($I$) flows through all resistors in series.
  • Equivalent Resistance ($R_{eq}$): Found by summing the individual resistances.
  • Formula: $R_{eq} = R_1 + R_2 + \dots + R_n$

• Parallel Connection

  • Resistors are connected across the same two nodes.
  • Characteristics: The voltage ($V$) across all parallel resistors is identical.
  • Equivalent Resistance ($R_{eq}$): Found via the reciprocal sum.
  • Formula: $\frac{1}{R_{eq}} = \frac{1}{R_1} + \frac{1}{R_2} + \dots + \frac{1}{R_n}$

• Voltage Divider Rule

  • Used for resistors in series to find the voltage across a specific resistor ($R_1$) without calculating current first.
  • Formula: $V_{R1} = V_s \times \frac{R_1}{R_1 + R_2}$

Kirchhoff's Laws

• Kirchhoff’s Voltage Law (KVL)

  • The algebraic sum of voltages around any closed loop in a circuit must equal zero.
  • Formula: $\sum V = 0$
  • In a simple series circuit: $V_s = V_1 + V_2$

• Kirchhoff’s Current Law (KCL)

  • The algebraic sum of currents entering a node must equal zero, or the sum of currents entering equals the sum of currents leaving.
  • Formula: $\sum I_{in} = \sum I_{out}$

Power and Energy

• Definitions

  • Electric Current ($I$): The time rate of flow of electrical charge ($Q$).
    • $I = \frac{dQ}{dt}$
  • Voltage ($V$): The energy transfer per unit of charge ($W/Q$).
  • Electric Power ($P$): The time rate of expending or absorbing energy.
    • Formula: $P = V \times I$

• Passive Sign Convention

  • Absorbing Power: Current enters the positive terminal of the element. $P > 0$.
  • Generating/Dissipating Power: Current enters the negative terminal (or leaves the positive terminal). $P < 0$.
  • If a calculation result for "absorbed power" is negative, the component is actually supplying power (e.g., a discharging battery).

Questions & Discussion

• Question on Practical Attendance: Can a student attend a different practical session if they miss their own?

  • Response: All practicals are highly occupied (usually full at 99 students). It is difficult to get a seat in another session. However, in later parts of the semester, some sessions may have fewer students. You can talk to the tutor, but it is highly unlikely and not guaranteed. It is best to stick to your allocated team of three.

• Question on Practice Exam Availability: Will practice exam style questions be removed once the next one is posted?

  • Response: No. Once materials (other than assessed quizzes) are made available, they will remain on Blackboard for the rest of the semester for review.

• Question on Circuit Grounding: What is the symbol at the bottom of the circuit diagrams?

  • Response: That is the ground (reference) symbol. It represents the node with zero potential ($0\,V$). If not explicitly shown, the bottom wire/node of the circuit is typically assumed to be the ground.

• Discussion on Complex Circuits: Integrating series and parallel elements.

  • Example Problem: A circuit with a $12\,V$ source, a $120\,\Omega$ resistor in series with a parallel combination of $200\,\Omega$ and $300\,\Omega$ resistors.
  • Solution Steps:
    1. Calculate parallel equivalent: $R_{parallel} = \frac{200 \times 300}{200 + 300} = 120\,\Omega$.
    2. Total resistance: $R_{total} = 120 + 120 = 240\,\Omega$.
    3. Use Voltage Divider Rule: $V = 12 \times \frac{120}{120 + 120} = 6\,V$ across the parallel set and the series resistor.