Electronics Fundamentals
Charge, current, voltage, resistance and power — the quantities every circuit is built on.
Before analysing any circuit you need a feel for a few basic quantities and the laws that connect them. Everything else in electronics builds on this page and its sub-topics.
| Quantity | Symbol | Unit |
|---|---|---|
| Charge | coulomb (C) | |
| Current | ampere (A) | |
| Voltage | volt (V) | |
| Resistance | ohm (Ω) | |
| Power | watt (W) |
Sub-topics (7)
Charge and Current
Electric current is the rate at which charge flows past a point.
Voltage
Voltage is the energy per unit charge between two points — the "push" that drives current.
Resistance and Ohm's Law
Ohm's law, V = IR, links voltage, current and resistance in a resistor.
Electrical Power and Energy
Power is the rate of energy transfer: P = VI = I²R = V²/R.
Kirchhoff's Laws
KCL: currents into a node sum to zero. KVL: voltages around a loop sum to zero.
Series and Parallel Circuits
In series the same current flows through every part; in parallel every branch has the same voltage.
Electrical Safety for Electronics
Current through the body is what hurts — understand the risks before working on circuits.
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