Section 3.3

Electrical Terminology

Potential difference, electromotive force, voltage, current, resistance, conductance, charge, conventional current flow and electron flow.

Notes

Free

Main ideas

EMF (electromotive force) is the driving force produced by a source, measured in volts. Potential difference (PD) is the voltage dropped across a component.
Current is the rate of flow of charge: I = Q / t, measured in amperes. One amp is one coulomb per second.
Resistance R opposes current and is measured in ohms (Ω). Conductance G is its reciprocal, measured in siemens (S).
Conventional current flows from positive to negative in the external circuit. Electron flow is the opposite — negative to positive.
⚠ Exam trap: questions deliberately switch convention. Read carefully whether conventional current or electron flow is being asked about.

Key formulas

Solved examples

A charge of 30 coulombs passes a point in 10 seconds. What is the current?
I = Q / t = 30 / 10 = 3 A.
A component has a resistance of 25 Ω. What is its conductance?
G = 1 / R = 1 / 25 = 0.04 S.

Mind map

Free

Quiz

Pro

This quiz is part of Engineer

Upgrade to unlock every quiz, mock exam and advanced simulation across all modules. Notes and mind maps stay free.