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The power supply

This page was translated from German with AI. It has not been checked by a native speaker. Original page in German

The power supply provides the energy for your circuits. With the knob you set how strongly it pushes the current – the number for that is the voltage in volts. Here you get to know the sockets, the two scales and the rules for switching on and rebuilding.
📄 Open worksheet (PDF, German)

The video

In the video you see the power supply from the front, once also from the back.

Subtitles are available in ten languages. Choose them at the bottom right of the video.

Contents of the video

  1. 0:00 Overview
  2. 0:14 Switching on
  3. 0:23 Direct voltage
  4. 0:40 Alternating voltage
  5. 0:59 How to start
  6. 1:14 Rebuilding
  7. 1:30 Short circuit
  8. 1:40 In short

The most important points

At the back are the mains cable and the switch: I means on, 0 means off.
At the back are the mains cable and the switch: I means on, 0 means off.

At the front, bottom left, are the red (plus) and the blue socket (minus). Direct voltage comes out there, from 0 to 20 V; you read it on the inner scale. The grey sockets next to them give alternating voltage from 0 to 25 V, with the same knob; for them the outer scale applies.

On the right there are fixed outputs for 6 V and 12 V alternating voltage. The knob changes nothing there.
On the right there are fixed outputs for 6 V and 12 V alternating voltage. The knob changes nothing there.

How to start

1. Knob to zero. 2. Connect the circuit. 3. Switch on at the back. 4. Turn up slowly until the value in your instructions. With the plug-in blocks never higher than 12 V.

Before every change switch off at the back; the knob stays where it is. If you change the circuit, for example from series to parallel, you turn the knob to zero first.
Before every change switch off at the back; the knob stays where it is. If you change the circuit, for example from series to parallel, you turn the knob to zero first.

Never connect plus and minus directly with a cable: that is a short circuit. There must always be a component in between, for example a lamp.

The worksheet

Here you can see the worksheet for the video (in German). The hints are printed upside down – turn the sheet only when you cannot get on by yourself. You can also open it as a PDF.

📄 Open worksheet (PDF, German)

The worksheet – Page 1
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The worksheet – Page 2
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The worksheet – Page 3
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Show the worksheet solutions
The worksheet – Page 4
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Try it yourself

Task

Three lamps light up in series. Now you are to connect them in parallel. Why is it not enough here to just switch the power supply off?

Show solution

In series the lamps share the voltage, in parallel each one gets the whole voltage. If the knob stayed where it is, each lamp would get a multiple – it could burn out. So: switch off, knob to zero, rebuild, switch on and slowly turn up again.

Keep learning with a language model

You are my physics teacher. I am learning about the power supply: red is plus, blue is minus, direct voltage on the inner scale, alternating voltage on the outer one, first knob to zero, then switch on, then turn up slowly, switch off at the back before every change. Ask me five short questions, one after the other, about situations at the experiment table. Always wait for my answer and then explain briefly.

How this was made: The idea and the choice of equipment are mine. A language model (LLM) drafted the script, the drawings, the worksheet and this page following my instructions. The devices are drawn from photos of our collection and from my own templates. The voice was generated with Qwen3-TTS, modelled on my own voice.

Limits and operation apply to the devices in our collection. If you work with other devices, follow what is written on the device and what your teacher says.

The videos, worksheets, texts and prompts in this series are licensed under CC BY 4.0: you may use, change and share them if you name the source.