Circuit Symbols: The Complete List and How to Read Them

An ammeter, which measures current in amps. It goes in series, so the current flows through it. Its resistance is very low so it has almost no effect on the circuit.

No. The dot is what signals a connection. A crossing with no dot means one wire passes over the other with no electrical contact.

A cell is a single pair of lines: one long and thin (positive), one short and thick (negative). A battery is two or more cells drawn in a row. In everyday speech people call a single cell a battery, but in physics the distinction matters.

A light-dependent resistor. The arrows point inwards because light is arriving. In bright light its resistance falls.

In parallel with the lamp — connected to the wire on each side of it, without breaking the circuit. Potential difference is a comparison between two points, so the meter must bridge those two points.

An LED, a light-emitting diode. The triangle and bar make it a diode, so current flows one way only; the two arrows pointing away show light being emitted. Arrows pointing in would make it an LDR instead.

The line represents the thin wire inside that melts when the current gets too high, breaking the circuit and protecting it. Without that line the symbol would just be a resistor.

It is the American convention rather than the one the IB and UK boards use, which is the plain rectangle. You should recognise a zigzag when you see it in an American textbook, but draw the rectangle in your own answers.

Circuit symbols are standard drawings that stand for electrical components in a circuit diagram. A rectangle means a resistor, a circle with an A means an ammeter, and so on. They are agreed internationally so that a diagram drawn by a student in one country can be read by an engineer in another. The modern set comes from the IEC 60617 standard, which is the basis for the symbols used by the IB and the UK exam boards.

Because a circuit diagram is about connections, not appearance. Two resistors can look completely different and behave identically; a drawing of the actual apparatus hides what matters and takes far longer to produce. A symbol strips a component down to one unambiguous mark, so anyone reading the diagram can see instantly what is connected to what.

A cell is drawn as one pair of parallel lines: a long thin line for the positive terminal and a short thick line for the negative. A battery is two or more cells drawn in a row. In everyday speech the AA you put in a remote is called a battery, but in physics that single unit is a cell, and a battery is several cells joined together.

For the IB and the UK exam boards it is a plain rectangle. The zigzag is the American convention, which you will meet in US textbooks, on many websites, and in a lot of electronics software. Both mean exactly the same component, but you should draw the rectangle in your own answers and be able to recognise the zigzag when someone else uses it.

Both are circles with a letter inside. A for ammeter, which measures current in amps. V for voltmeter, which measures potential difference in volts. The letter is the only difference between the two symbols, so read it carefully before answering a question about either.

In series, so the current it is measuring passes straight through it. An ammeter has a very low resistance for exactly this reason: it has to sit in the circuit without changing the current it is there to measure. Put one in parallel across a component and it short-circuits that component.

In parallel, connected across the component you are measuring. Potential difference is the difference between two points, so the meter must touch both. A voltmeter has a very high resistance so that almost no current is diverted through it. Put one in series and it blocks the circuit.

A resistor rectangle with a diagonal arrow drawn across it. The arrow is the slider you move by hand to change the resistance. A potentiometer looks similar but has a third connection — an arrow pointing into the rectangle from one side — because it taps off a fraction of the voltage rather than simply adding resistance.

A resistor rectangle inside a circle with two arrows pointing towards it, showing light arriving. In bright light its resistance falls; in darkness it rises. That is the opposite of what most students guess, and getting it backwards inverts every conclusion that follows. LDRs are what make street lights come on at dusk.

A resistor rectangle with a line running up and across it at one end. In the type you meet in exams — a negative temperature coefficient thermistor — resistance falls as temperature rises. They appear in thermostats, fire alarms and engine temperature sensors.

Look at the arrows and at the body of the symbol. An LED is a triangle and bar — a diode — with two arrows pointing away, because it gives out light. An LDR is a rectangle — a resistor — with two arrows pointing towards it, because light falls on it. Arrows out means emitting; arrows in means detecting.

In the direction the triangle points. The triangle acts as an arrowhead showing the forward direction, and the bar at its tip is the barrier that blocks current trying to come the other way. That direction is conventional current, from positive towards negative.

A circle with a cross inside it, drawn so the four arms of the cross reach the edge of the circle. It is sometimes called a bulb or an indicator lamp. Do not confuse it with the meters, which are circles containing a letter.

A solid dot marks a junction — a point where wires are electrically joined. If two wires cross with no dot, they are not connected; one simply passes over the other on the page. This single convention changes what a diagram says, so put a dot at every real connection and leave crossings clear.

A rectangle with a line drawn through it from one wire to the other. The line represents the thin strip of wire inside that melts when the current rises too high, breaking the circuit and protecting the rest of it. Without that line the symbol would just be a resistor.

Yes. The IB Diploma, GCSE and A-level all use the same IEC-based set, so the symbols on this page serve all three. The difference between the courses is how many you are expected to know and what you are asked to do with them: GCSE focuses on recognising symbols and building simple circuits, while IB and A-level add potential dividers, sensing circuits and more demanding analysis. The drawings themselves do not change.

The twenty-five on this page cover everything that appears on IB, GCSE and A-level papers. If you are short of time, learn the supply symbols, the switch, the resistor family, the two meters and the lamp first — those make up the great majority of the circuits you will be asked to read or draw.