Lesson 1 - Voltage, Current, Resistance (Engineering Circuit Analysis)

The lecture introduces the basics of circuit analysis for engineering students and enthusiasts, emphasizing the importance of understanding electrical circuits. The instructor is excited and aims to make the complex content accessible. Key components to be studied include basic concepts like voltage, current, and resistance, and how to analyze circuits. The approach will start with fundamentals and progress to more complex ideas, preparing students to tackle real-world circuit analysis.

A basic definition of an electric circuit is provided: a circuit is a closed loop that allows electricity to flow. This concept is illustrated using a battery and wire analogy. The concept of electric current is then introduced as the flow of electrons in a circuit, akin to water flowing in a stream. The electrons' movement is critical to circuit functionality, and understanding this flow is foundational for analyzing how circuits work.

The discussion continues with an explanation of electric current, emphasizing that electrons move within the circuit, flowing from negative to positive ends. This movement is like a chain reaction at nearly light speed. For engineering purposes, current is often conceptualized as positive charges moving in the opposite direction of electron flow, simplifying calculations and avoiding negative signs in equations.

The concept of electric current is explored further with a distinction between electron flow and the convention used in circuit engineering, known as "hole current," which describes positive charge movement opposite to electrons. This convention helps simplify circuit equations. The unit of current is the ampere (amp), measuring charge flow over time. The concept of amps is linked to everyday applications, indicating power levels in electrical devices.

The concept of voltage is introduced as the "push" that causes currents to flow, measured in volts. Voltage is crucial for overcoming resistance and enabling current flow in circuits, analogous to air pressure moving through a straw. The potency of voltage relates to its ability to move electrons through conductors. Higher voltage implies more potential for current flow, distinguishing it from current, which is the actual movement of electrons.

Resistance is explained as the opposition to current flow in an electrical circuit, measured in ohms. The analogy of blowing air through different sized tubes helps illustrate how resistance affects current flow — the larger the tube, the less resistance. The discussion highlights the importance of resistance in controlling current flow and its role in circuit functionality. Resistance, voltage, and current are interconnected concepts critical for understanding circuitry.

Metric prefixes like milli, micro, kilo, and mega are applied to all units (voltage, current, resistance) to accommodate various magnitudes encountered in circuits. The lecture covers the concepts of direct current (DC) and alternating current (AC), explaining their differences, usages, and implications. DC is constant, typically from batteries, while AC varies, like household electricity, highlighting the historical and practical reasons for these differences.