Resistivity
Question:
I know that the
resistivity of an insulating paper is 10x10
9 Wm.
But how do I set up an experiment to find out the resistivity or
to prove it is correct or not ?
Answer:
The paper that you have
apparently has a resistivity of 10x10
9Wm or 10000
M
Wm.
Lets also assume that you have a digital meter
that will enable you to measure a resistance of around 10 M
W.
(this is quite normal for the meters available in Britain now).
The connection
between resistance and resistivity is:
Resistance = resistivity x length/area.
Now
if the resistance is 10
7 W, the resistivity 10
10 Wm and the paper is 10
-4 m thick then you would need a
piece 0.1 square metres in area with contacts taped to the two faces.
Possible!
Alternatively using a pico ammeter (currents as low as 10
-10 A.
You could tape the contacts to the two faces and simply measure the current passing
through the paper with a variety of applied voltages.
So for a piece of your paper 1
cm square with a resistance of 10
10W the current for
a 12V input would be 12/10
10 = 1.2 nA (12x10
-10 A) – easily within the
range of the meter I have looked at.