Power Lines

Produced by the National STEM Learning Centre and the Institute of Physics, this video is aimed at teachers. Alom Shaha shows a demonstration that can be used to illustrate power transmission and why high voltages are used to minimise power loss.

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Stuart Billington

Again, really nice and clear and concise, with due attention to safety.

I don't have a fixed low voltage ac supply and have to resort to a variable dc/ac powerpack instead. If you do this, you must must must (!) ensure you're using the ac terminals as the changing emf as the dc goes from 0V to 2V can cause an extremely high induced pd across the output terminals of the transformer.


Great stuff. As Stuart says, clear & concise: good for new and non-specialist teachers.

Now how about a related demonstration on AC vs DC as regards energy delivery? 2 identical bulbs with dual beam CRO across each (or failing that DC and AC voltmeters) . Battery lights one bulb, the other has a variable AC or power sig gen which is adjusted to give the same brightness. across each, whilst the CRO traces are monitored. For GCSE good for showing "DC equivalent voltage" is about 70% of peak pd, the former being what is quoted as the AC "voltage", the strict average being zero. For A-level can be made more quantitative to consider RMS values. If using sig gen for the AC, the same set up can be used to show situation with sqaure, sawtooth & triangular waveforms.


Very good video! Nice way to get the message across. Well done!

Carol Davenport

This is a really useful video for teachers, technicians and students. When you only get an experiment out once a year, it will be helpful to have a reminder about how to set it up. Showing the measurements also mean that it can be used for students who missed the lesson.


nice simple demo, looks easy to use and well explained