Electronics Common pitfalls

Use this as a debugging checklist for circuit problems.

Voltage does not flow

Voltage is a difference in energy per unit Charge. Current flows. Saying “voltage flows through the resistor” usually hides a conceptual error.

Current is not used up

In a series loop the same current passes through every component. Components can reduce voltage/energy per charge, but charge is conserved.

Ground is a reference

Ground is often just the node chosen as $0\mathrm{V}$. It is not automatically “where current goes,” and it is not always Earth ground.

Electron flow vs conventional current

Conventional current points in the direction positive charge would move. Electron drift in metal is opposite. Do not switch conventions halfway through a problem.

Ohm’s law is not universal

$V=IR$ is excellent for ideal resistors and many wires, but not for every component. Diodes, LEDs, lamps, thermistors, batteries, and transistors can have nonlinear behaviour.

Series vs parallel confusion

Series means same current. Parallel means same voltage. If you remember only the formula without this meaning, it is easy to combine components incorrectly.

Power sign mistakes

With the passive sign convention, current entering the positive terminal means $P=IV$ is absorbed. If current leaves the positive terminal, the device supplies power.

Unit slips

Track units: $\mathrm{A}=C/s$, $\mathrm{V}=J/C$, $\Omega =V/A$, $\mathrm{W}=J/s=\mathrm{VA}$.

Related: Electronics Equations and definitions, Electronics Examples, Electromagnetism MOC.