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Measuring Electrical Conductivity
Name: Jessica
Status: Student
Grade: 9-12
Location: OH
Country: United States
Date: January 2007
Question:
How do you test the electrical conductivity in metals?
Replies:
Hi Jessica
Conductivity can be inferred by measuring the resistance. If you hook
up a sample to be tested to a voltage source and measure the current
going through the sample and the voltage across the sample, the
resistance can be calculated from Ohm's law: R = E/I where R is
resistance in ohms, E is voltage in volts and I is current in
amperes. Once you have resistance, you can calculate resistivity.
Resistivity is a factor, which when multiplied by the length of the
sample and divided by its cross-sectional area, will yield the
resistance. Conductivity is the reciprocal of the resistivity. The
higher the conductivity, the easier it is to pass a current through
the material.
Hope this helps.
Bob Froehlich
Hi Jessica,
Electrical resistance is tested with an Ohmmeter. This is a
simple device that sends a measured current through a sample
of the metal in question, and measures the voltage required
to "push" this current through the metal. Ohm's Law states
that the resistance (in Ohms) of a conductor is equal to the
voltage (in Volts) required to drive a resulting current (in
Amperes). To give an example, let us say that you have a
sample of a long thin metal wire. You attach electrical
contacts to each end and apply a voltage of (let us say) 1
Volt between each end of the wire. This 1 Volt difference
from one end of the wire to the other, causes a current to
flow down the wire. If the resulting current was 1 Ampere,
then the resistance of the wire is 1 Ohm. If only 0.5 Ampere
had resulted, then the wire's resistance would be 1 Volt
divided by 0.5 Ampere, or 2 Ohms.
Regards,
Bob Wilson
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Update: June 2012
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