Drawing Electrical Circuits

Why use circuit diagrams?

Real circuits can look messy. A circuit diagram uses standard symbols joined by straight lines to show how components connect. It does not show what the parts look like or exactly where they sit. It only shows how they are connected.

Standard circuit symbols

Rules for drawing a good circuit diagram

1. Use a ruler. Draw wires as straight lines with square corners.
2. Use the standard symbols only. Do not draw pictures.
3. Make sure there are no gaps in the loop, unless there is an open switch.
4. Do not draw a component on a corner. Put it on a straight side.
5. Show where wires join with a solid dot. Wires that cross without a dot are not connected.
6. Draw ammeters in line with the component. Draw voltmeters beside the component, joined on either side of it.

A simple circuit

Follow the loop with your finger. From the cell, through the lamp, through the ammeter, through the switch, back to the cell. One complete loop. Close the switch and the lamp lights.

Short circuits

A short circuit happens when current finds an easy path with almost no resistance, skipping the components. The current becomes very large. Wires get hot, batteries drain fast, and there is a risk of fire. Fuses and circuit breakers are there to cut the power if this happens.

Quick summary

• Circuit diagrams use standard symbols and straight lines to show connections.
• Cell: long line positive, short line negative. A battery is several cells.
• Draw with a ruler, square corners, no gaps, dots where wires join.
• Ammeters go in series. Voltmeters go in parallel across a component.
• A fuse melts to break the circuit if the current gets too high.
• A short circuit is a low-resistance path that causes dangerously large current.

Quiz