Circuits: an interactive basic electronics course

Circuits is an interactive basic electronics course that builds from a single loop to digital logic. Its 28 short sections cover voltage, current and resistance, Ohm's law, series and parallel circuits, voltage dividers, capacitors and RC timing, LEDs and transistors, logic gates, truth tables, combining gates and Boolean expressions, with a practice question every couple of sections.

The first half is the analogue electronics behind every gadget; the second half is the digital logic inside every computer. Together they are the groundwork for Arduino and Raspberry Pi projects.

What the course covers

Analogue circuits

Ohm's law, V = IR, links voltage, current and resistance and runs through everything else. In series the same current flows through every part and resistances add; in parallel every branch gets the full voltage and the total resistance falls. Two resistors in series make a voltage divider, giving a fraction of the supply, which is how many sensors are read.

Capacitors and timing

A capacitor stores energy and charges through a resistor along a curve, not a straight line. The time constant RC sets the pace: after one RC the capacitor reaches about 63% of the supply voltage.

Here x is time measured in time constants (RC) and y is the capacitor's voltage. It rises quickly at first, then levels off towards 5 V.

Digital logic

Logic gates take binary inputs and give one output: AND needs both inputs on, OR needs at least one, NOT flips its input, and NAND can build every other gate. Truth tables list every input combination, and Boolean expressions such as A · B + C describe whole circuits.

Try a question from the course

Rearrange V = IR for the unknown. A 9 V supply across a 450 Ω resistor gives a current of I = V ÷ R = 9 ÷ 450 = 0.02 A, or 20 mA.

Now solve a new Ohm's law problem, then press Mark to check your answer in the course.

Who this course is for

• Beginners in electronics who want to understand the components in a starter kit.
• GCSE and A-level students revising circuits in physics, or logic gates and Boolean expressions in computer science.
• Makers heading for Arduino, ESP32 or Raspberry Pi projects.

What you need to know first

The course page suggests Electricity first, for charge, current and voltage. You also need to rearrange simple formulas and work with fractions for parallel resistors.

How long it takes

There are 28 sections and most take a few minutes. Learners without a plan can open two sections of a course a day, in order, so the whole course takes 14 days. A plan removes the daily limit and lets you go straight to any topic, such as logic gates. Our conditional and logical statements guide shows the same AND, OR and NOT logic in code.

Read next

Computer Science · Data and logicLogic gate simulator: build circuits, see the truth tableBuild logic circuits from AND, OR, NOT, NAND, NOR and XOR gates, flip switches and watch the signals, with a live truth table and an expression per lamp.