Switches and circuit symbols
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The idea
If you want to write down a circuit, you do not have to draw cables and lamps. Every part has a short circuit symbol. That way people all over the world read the same diagram.
What to remember
- Switch
A switch opens or closes the circuit. Closed, the current flows; open, none flows.
- Circuit diagram
A circuit diagram shows a circuit with circuit symbols instead of drawings of the parts.
The most important circuit symbols. With the open switch the line is broken; with the closed switch it is unbroken. Labels: 1 battery, 2 lamp, 3 open switch, 4 closed switch.
Source: https://github.com/lernapps/elektrizitaet. Licence: CC0-1.0.| Part | How to recognise the circuit symbol |
|---|---|
| Battery | two bars, a long thin one and a short thick one |
| Lamp | a circle with a cross inside |
| Open switch | a line with a gap; the current does not flow |
| Closed switch | an unbroken line; the current flows |
Example
A circuit diagram in words
A circuit diagram shows: battery, then a switch, then a lamp, then back to the battery. If the circuit symbol of the switch is unbroken, the switch is closed and the lamp lights up. If it shows a gap, the switch is open and the lamp stays dark.
Practice
Exercise
Solution
Right answer: a circle with a cross – Lamp; two bars, a long one and a short thick one – Battery; a line with a gap – open switch
The circle with a cross stands for the lamp, the two bars for the battery, and the gap in the line shows an open switch.
More on it:
Exercise
Solution
Right answer: The statement is false.
The gap means that the circuit is broken there. The switch is open and no current flows.
More on it:
Exercise
Solution
It is closed. right answer
Only when the switch is closed is the whole circuit closed, so that the current can flow.
It is open.
With an open switch the circuit is broken and the lamp stays dark.
You cannot tell.
Yes, you can. If the lamp is lit, the circuit must be closed everywhere, including at the switch.
The lamp only lights up when the current can flow through the switch. So it must be closed.
More on it:
Task no. 1
Task no. 1
Build a circuit with one lamp and one switch. You should be able to switch the lamp on and off with the switch.
The circuit board is a circuit with two places. You choose lamp, switch or wire, tap a place and then switch the power on.
Solution
The lamp on one place, the switch on the other: the switch turns the lamp on and off.