# Science fair project guidance help

Discussion in 'Electronics Homework Help' started by CedarPark, Jan 18, 2012.

1. ### CedarPark

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Jan 18, 2012
I'm in 8th grade, been studying electronics for 2 months, and decided to do a physics based project. I want to know how temperature affects the resistance of a wire, and this is my plan. I would like constructive criticism.

3 1.5 volt batteries in a battery case will be connected to 1 meter of copper wire that will all be connected to a multimeter where I will have it measure ohms.

However, there are still some concepts I need help understanding. one website recommended to wrap the wire with insulation tape around a PVC pipe (i don't know what a PVC pipe is). It also said to use jumper wires with crocodile clips for connection.

It also said to use an infrared thermometer and a paper knife for stripping a wire (which I don't get). I am fairly new to science experiments and this is my second hands on experiment.

2. ### Harald KappModeratorModerator

11,806
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Nov 17, 2011
You can calculate the resistance of a wire from its parameters (material, length, diameter): http://hyperphysics.phy-astr.gsu.edu/hbase/electric/resis.html

You can calculate the temperature dependency from the so called temperature coefficient: http://www.cirris.com/testing/temperature/copper.html

When you do this, you will notice that 1 m of copper wire has a fairly low resistance (depending on its diameter / wire gauge). In order not to drain your batteries too fast you will need either a very long wire or a very thin wire.

PVC is a kind of plastic.

Stripping a wire means removing the insulation. There are basically two types of wire:
1) with plastic insulation
2) with enamel insulation. The latter goes by the name of magnet wire, too.

I can only guess but I think the project calls for type 2 insulation. The thin enamel allows thightly wound layers of wire on the tube. Beware: even if the wire looks like pure copper, it will not conduct reliably if you attach crocodile clips without stripping the enamel at the point of contact.

Harald

3. ### Aggie

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Jan 11, 2012
Your experiment idea is nice and simple.

I would suggest magnet wire (enamel coated), which you can buy on ebay by the roll.

I wouldn't used PVC pipe since it will be slow to transfer heat to your wire. I would wrap the magnet wire around galvanized pipe or copper pipe. The galvanized pipe is cheaper. Check with a local/mom&pop plumbing supply. Tell them what you are doing for your science fair project and they might be willing to give you some materials as well.

Harald is right in that you will need a long piece of wire wrapped around the pipe. Research ways of making a coil out of magnet wire. Google should give you tons of references to this. If you coat the wire wrapping with an enamel or epoxy that is thermally conductive, it will help to transfer the heat that you want.

Cap one end of the pipe and you can fill it with what ever temperature water you want. You could, very carefully and with adult help, fill it with dry ice chips to really drop the temperature. BUT DONT ADD WATER WITH THE DRY ICE CHIPS!!!

If you happen to live near a university or college, contact a chemistry professor. They MIGHT be willing to help and fill your pipe with liquid nitrogen. haha.

Good luck!