Introductory Circuit: DC & AC

Introductory Circuit is a step-by-step course in circuit analysis for beginners: 41 lessons that take you from charge, current and voltage to DC circuits, network theorems, capacitors, inductors and AC circuits.
Each lesson explains the idea in plain words, solves worked examples with every step shown and ends with practice questions. 53 original circuit diagrams and graphs, and it all works offline.

Learn electric circuits the way a first circuits course teaches them: understand why a circuit behaves as it does, then calculate it. The same circuits come back in several lessons and are solved with different methods, so you can see how series-parallel reduction, mesh analysis, nodal analysis and Thevenin's theorem connect.

What you will learn

• Charge, Current and Voltage: atoms and electric charge, electric current, voltage and potential difference, voltage and current sources
• Resistance: resistance and resistivity, temperature and special resistors such as thermistors, resistors and the colour code
• Ohm's Law, Power and Energy: Ohm's law, electric power, energy, kWh and efficiency
• Series Circuits: Kirchhoff's voltage law, the voltage divider, real sources and loading
• Parallel Circuits: Kirchhoff's current law, the current divider, open and short circuits
• Series-Parallel Networks: the reduce-and-return method, series-parallel worked examples, ladders and bridges
• Methods of Analysis: source conversion, the branch-current method, mesh analysis and nodal analysis
• Network Theorems: superposition, Thevenin's theorem, Norton's theorem, maximum power transfer
• Capacitors and Inductors: capacitors, RC charging and discharging, inductors, RL transients
• Introduction to AC: sine waves, RMS and average values, phase and phasors, reactance, impedance and AC power
• Measurement and Problem Solving: using a multimeter, electrical safety, a problem-solving strategy for any circuit

Features
• 41 lessons in 11 sections, in a sensible learning order
• 109 worked examples with every step shown
• 133 practice questions with tap-to-reveal answers
• 53 original drawings: circuit diagrams, graphs, waveforms and phasor diagrams
• Clear, sharp formulas on any screen
• Search all lessons from the home screen
• Previous and Next buttons to work through a section in order
• Dark mode that follows your phone's setting
• Works offline, no account needed
• Available in 8 languages: English, Español, Português, Français, Deutsch, العربية, हिन्दी and Bahasa Indonesia

Who it is for
• Beginners who want to learn basic electrical circuits from the start
• Students in a first electric circuits or circuit analysis course in electrical or electronic engineering
• Physics and technology students meeting DC and AC circuits, Kirchhoff's laws and Ohm's law
• Apprentices and electronics hobbyists who want to understand a circuit, not just memorise a formula

More than a formula sheet, Introductory Circuit is a course: it teaches the reasoning behind each method so you can solve circuit problems on your own.

Introductory Circuit is an independent study aid. Content is checked against OpenStax University Physics Volume 2, OpenStax College Physics 2e, the NIST SI Brochure, NIST CODATA 2022, IEC standards and standard circuit analysis textbooks. It is not affiliated with any exam board, textbook publisher or standards body. Work on mains equipment only if you are qualified.

Recent changes:
Improved Arabic display: maths, codes and English names in tables now read in the right order.