how do you set up a conductivity test to test various metals?

Question

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Answer 1

You need to precisely measure very small resistance values. This is not really possible with a standard DVM. There are mircoOhm meters available from companies like Agilent but these are expensive.

You can use a Whaet Stone Bridge circuit to compare a known resistance to another. The circuit is very easy to build and uses an amp meter to determine when the circuit is balanced.

You could use a lenght of copper wire with known properties (from a wire gauge table) and compare wires of different materials. Null the metter by changing the lenght of unknown resistance wire connected to teh Wheat Stone circuit

Answer 2

There are many different ways, but they almost all are based on the following approach:

Use a sample of the material you want to determine the conductance of. It should have a constant cross-section, like a cylindrical wire or a parallelpiped. You need to attach 4 wires to the sample along the length. The 2 outer wires are used to apply a know current through the sample. The inner 2 wires are used to measure the voltage across the sample. The reason different wires are used for current and voltage is to remove the resistance associated with contacting the wires to the sample. This is called the Kelvin method. From this, the conductance sigma can be calculated:

sigma = I/V.

Using the cross sectiton A and length between voltage contacts L, the conductance SIGMA can be calculated as follows:

SIGMA = sigma L/A

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Answer 3

Use wires of precisely the same size and length, and compare he conductivity.