# Circuits – Calculating resistance/conductance etc

**1. The problem statement, all variables and given/known data**

Source with voltage 4.25mV is ran along a 10cm long cylindrical copper conductor which has a cross sectional radius of 0.8mm. If the current was measured at 5A flowing through the conductor calculate: the resistance and conductance of the conductor and the resistivity and conductivity of the material the conductor is made from.

**2. Relevant equations**

The only equations we were given last week which is supposed to refer to this problem type are:

[tex]

I=\frac{Q}{t} \\

Q=ne \\

I=\frac{ne}{t} \\

I=frac{neAl}{t}=neAv_d \\

v_d=\frac{I}{nAe} \\

J=\frac{I}{A}=nv_de \\

\rho=\frac{E}{J} \\

\rho=(\frac{V}{I})(\frac{A}{l}) \\

R=\frac{V}{I}=\frac{\rho l}{A} \\

**3. The attempt at a solution**

For the resistance i have done:

[tex]

R=\frac{V}{I}=\frac{0.00425}{5}=0.00085Ω

[/tex]

For the conductance I looked it up that its the inverse so I just did

[tex]

\frac{1}{0.00085}=1176.47Ω^{-1}\\

[/tex]

for the resistivity i have done

[tex]

\rho=\frac{RA}{l} \\

\rho=\frac{(0.00085)(\pi 0.0088^2)}{0.1}=2.07\times 10^{-5} \\

[/tex]

It is the conductivty that is confusing the hell out of me, dont even know where to start.

Any help is really appreciated. Thanks.

http://ift.tt/1jaFa9Z

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