Electromagnet vs magnet for towing behind bike to pick up nails

Hello. I'm seeking a little help ascertaining the viability of an ebike battery powered electromagnet that is towed behind a bicycle for picking up nails/screws/etc.
and wondering how that would compare to a non-powered magnet.
I was thinking roughly 24" long and maybe 1 or 2" wide, 2-3" off the ground, minimum speed to make it worth it would be about 5mph (for bike trailers, since they tend to go slow.)

Any assistance you can give would be great, as I am interested in trying to make a magnet sweeper to help clean the roads up.
Thanks for any help you can give!

I question the point of having the magnet behind the bike. Seems to me that your tire might pick up the nail first, leaving you with a flat tire. Perhaps you want  to catch the  nails before you run over them. You might want  to  think about the  application before thinking  about the design.

Hi Brian-I think you would come out way ahead by using several neodymium magnets instead of an electromagnet. Put the magnets behind a nonmagnetic (maybe aluminum) hinged plate, so when it gets full of nails you can swing it open (away from the magnets) so the nails will drop off. While an electromagnet has the advantage that you can turn it off, the neodymium magnets will be cheaper, lighter, and have a virtually unlimited "run time".P.S.- Make sure you've got "flat free" tires on the bike!-Rick  

Perhaps you want  to catch the  nails before you run over them. You might want  to  think about the  application before thinking  about the design tellthebell.