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# Powering lights from speed bumps watch

1. Hey! I have a task to produce a model to generate electricity from a speed bump. My initial thoughts are having a magnetic field covering the speed bump and when the car moves over the bump, the bump compresses and therefore moves through the magnetic field to generate an emf.

We know the emf across the speedbump= (BxL)/t where B is the magnetic field strength, x is the distance moved through the field, L is the length of the speedbump and t is the time to compress (found from suvat of the car under gravity falling a set distance).

From google, I know a street light requires 80W of power. To be lit for 10 hours it needs 80*60*60*10=2880000J of energy.

Ideally I now want to find out if this is feasable by looking at the strength of the magnet required. To do this, I would need to find the emf across the speed bump and then can solve for B but surely I need to include the fact the light needs to be on for 10 hours and needs that much energy so how can I relate that to the emf across the speedbump?

Thanks for any help!

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Updated: October 20, 2015
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