Circuit symbols

We use circuit symbols to draw diagrams of electrical circuits, with straight lines to show the wires. The diagram shows some common circuit symbols.

Switch - two circles connected by a line. If the line connects the circles, the switch is closed. If it is only connected to one circle the switch is open. A cell - two vertical lines, one thin and one shorter and thicker. A battery - two cells connected by a dotted line. A lamp - a circle with a cross in it. A voltmeter - a letter V inside a circle. An ammeter - a letter A inside a circle. A resistor - a rectangle. A variable resistor - a rectangle with an arrow through it at 45 degrees. A motor - a letter M inside a circle.Some common circuit symbols

Cells and batteries

The symbol for a battery is made by joining two more symbols for a cell together.

Circuit symbols for cell and battery.Make sure you know the difference between these two symbols

Think of what we usually call a single battery, like the type you put in a torch. In physics, each of these is actually called a cell. It is only when you have two or more of these cells connected together that you call it a battery. Do not confuse electrical cells with the cells in living organisms.

Circuit diagrams

The idea of a circuit diagram is to use circuit symbols instead of drawing each component in the circuit. Always try to make the wires straight lines. Do not be tempted to make them wiggly because the whole point is to make it easier to see what is connected to what.

Here you can see how the symbols for a cell and a lamp look in a circuit diagram:

Shows a circuit with a cell and a lamp, and then the same circuit drawn as a circuit diagramYou could make the circuit by laying out the cell and lamp on the table as shown in the circuit diagram, then joining them using wires

If you have to draw a circuit diagram:

  • draw the circuit symbols first, then
  • draw all the wires

If you have to draw wires to join circuit symbols that have been drawn for you already, use a ruler and do not let the wires cross each other.