help on a physics project...electromagnet

[dave127]

in my physics class, we have to build a sleigh that will drop a 10g "bag of gifts" into an small, soup can chimney. it has to do this while riding on an overhead track made out of 1/8" aviation cable...the whole project has to weigh under a pound, and the object is to get it down the 10 m track as fast as possible while still remaining accurate...i have figured out that i will use an electromagnet to hold the bag and drop it when it hits a trip point on the track (insluated with electricial tape)....we will be sending our electric current through one pulley, onto the wire, and back down to the other pulley so that when it hits the tape, the current will cut off, and the bag will drop...

my question is, what kind of battery and other such things should i use to make an electromagnet strong enought to hold the bag while moving down the track, but not so powerful that the nail or whatever i end up using retains its magnetism and doesnt drop the bag....thanks guys

dave

 

[atrowe]

Nine volt battery would probably be your best bet. It's light and provides a lot of power, but won't last very long. Maybe a few lithium watch cells in sequence would be another alternative.

 

[dave127]

hey...thanks for the reply, but i should have mentioned, i tried a 9v already...too powerful...it holds the charge like 30 secs after i cut the power, so its a no go...but a d-cell is too weak...are there any other alternatives??? i have a week and a half to go still, so im in no hurry...thanks

Dave

 

[notfred]

<< hey...thanks for the reply, but i should have mentioned, i tried a 9v already...too powerful...it holds the charge like 30 secs after i cut the power, so its a no go...but a d-cell is too weak...are there any other alternatives??? i have a week and a half to go still, so im in no hurry...thanks

Dave >>



2 1.5 volt batteries. (AAA, AA, C, D are all 1.5 volt). if that's not enough, use 4.

 

[Linflas]

You may want to check out some of those little flat camera batteries. I think some of them put out 1.5 VDC each and would not weigh much if you needed to put a couple in series to up the voltage. I used to use 6VDC lantern batteries for electromagnets in projects so you may want to try around that voltage.

 

[Ameesh]

i'd use a couple of AAA in series, they are 1.5 V each i dont know how much voltages the watch baterries are, and there are B bateries which are pretty small but you cant find the everywhere.

 

[MajesticMoose]

couldn't you just adjust the insulated portion to account for the 9v?

m00se

 

[AnthraX101]

Yeah, I second the idea of using regular 1.5 v batteries. AA (AAA if size/weight is that much of a consideration) or if size/weight doesn't matter, then use D's. If it's still too strong, start adding voltage drop circuts

Armani

EDIT: Oh, and if you use a larger core, it will not stay magnitised as long.