Science Buddies: "Ask an Expert"

So my son had this idea for his science project to see which of 3 vegetable transfer more electricity.

The problem:

He needs the electromagnet to be able to attract a washer from 2 - 4 inches away, but we can only get it to hold things you attach to it.

what we have tried:
we have tried the following items in every combination I can think of, including double wrapping the wire.

3" hardened steel bolt
12" Ferrous metal bar
12 gauge wire
24 gauge wire
9-volt battery
2x D-cell batteries in series
1 hardened steel nut
1 hardened steel washer

He has procrastinated the project, as kids often do, and it is due tomorrow. We have been unable to get past the electromagnet part, and I am trying to guide rather than give the answers. The main thing at this point is that I want to have the materials he needs to make it work on hand, instead of buying a dozen different things and hoping one fixes the issue.

Any help at all would be appreciated, I am thinking about using a 12V powerwheel battery to try and boost the magnet.

Hi Tenchu,
You are definitely on the right track with increasing the voltage. Please do note though that it really is the current that determines the field strength. (Ampere's Law) To make a long story short, you can either increase the voltage so that you get higher current, or you can lower the resistance (increase the wire size or parallel the wires).

Hope that helps. Good Luck!
Willey