Alternating Current
Electricity and Magnetism
The waveform of AC on a demonstration oscilloscope
Practical Activity
for 14-16
Demonstration
A simple qualitative demonstration of the varying voltage of an alternating supply.
Apparatus and Materials
- Power supply, AC, low voltage variable
- Leads, 4 mm, 2
Health & Safety and Technical Notes
Read our standard health & safety guidance
Procedure
- Set the oscilloscope with the volts/cm switch to 1, the time-base control to 1 ms/cm, and the AC- DC switch to AC.
- Set the output of the power supply to 2 V (approx).
- Connect the AC terminals of the power supply to the input terminals of the oscilloscope. Adjust the time-base anticlockwise until four or five cycles of the waveform appear on the screen. The pattern traced on the screen should remain fixed in position.
Teaching Notes
- This demonstration is largely to provide a talking point.
- Point out the sine wave nature of the waveform.
- You could show the output of other sources of AC in the same way, e.g. the output of a transformer made using C-cores and ready-made coils, or with hand-wound coils. Comparisons of the input and output voltages could be made.
This experiment was safety-tested in October 2006
- A video showing how to use an oscilloscope:
