

Measuring Electrical Conductivity
Name: Jessica
Status: Student
Grade: 912
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 crosssectional 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

