Overview
This lecture introduces the basics of electrical circuits, key circuit components, and the definitions of current, potential difference (voltage), and resistance, as well as the conventional direction of current flow.
What is a Circuit?
- An electrical circuit is a closed loop with a power source and a path for electrons to flow.
- Simple circuits can be represented using circuit diagrams.
Key Circuit Components and Symbols
- The symbol for a cell (single power source) is a long and short line; a battery uses two cell symbols.
- A filament lamp symbol represents a small light bulb that lights up when powered.
- A switch symbol shows a component that opens (breaks) or closes (completes) the circuit.
Potential Difference, Current, and Resistance
- Current (I) measures the flow of electrons around the circuit and is measured in amperes (A).
- Potential difference (V), also called voltage, is the force driving electrons around the circuit; measured in volts (V).
- Resistance (R) opposes the flow of electrons, similar to a blockage in a pipe; measured in ohms (Ω).
Direction of Current Flow
- The longer line on a cell/battery symbol marks the positive terminal, and the shorter line is the negative terminal.
- Electrons flow from negative to positive, but conventional current flows from positive to negative.
- For exams, always assume current flows from positive to negative terminal.
Key Terms & Definitions
- Circuit — a closed loop allowing electrical current to flow.
- Current (I) — the rate of flow of electrons, measured in amperes (A).
- Potential Difference (Voltage, V) — the force pushing electrons, measured in volts (V).
- Resistance (R) — opposition to current flow, measured in ohms (Ω).
- Conventional Current — the direction current is considered to flow (positive to negative).
Action Items / Next Steps
- Review and memorize the main circuit symbols.
- Prepare for more detailed videos or lessons on additional circuit components.