Electronics Key concepts
Electronics is circuit-level electromagnetism: use components to control Current, Voltage, energy transfer, and information.
Node, branch, loop
A node is a set of connected points treated as the same voltage when wires are ideal. A branch is one path between nodes. A loop is any closed path. Circuit analysis is mostly bookkeeping across nodes and loops.
Ideal wires and components
An ideal wire has zero Resistance, so every point on that wire is at the same potential. Real wires have small resistance, capacitance, and inductance, but ideal wires are a useful first model.
Conventional current
Circuit arrows use conventional Current: the direction positive charge would move. Electrons in metals drift the opposite way. Use the conventional direction consistently and signs will work.
Passive sign convention
If current enters the positive-voltage side of a passive element, the element absorbs power: . Resistors absorb power and heat up. Sources can deliver power when current leaves their positive terminal.
Ground/reference
“Ground” is usually a chosen reference, not a magic sink for charge. Voltage is always measured between two points.
Lumped-circuit assumption
Intro circuits assume component sizes are much smaller than signal wavelengths, so voltages/currents update “everywhere” fast enough to ignore wave propagation. This breaks down in high-speed electronics and RF design.
Parent map: Electromagnetism MOC.