# The electrical resistivity of copper is 1.68*10^-8 ohm*m. What is the conductance of a copper wire that is 10 m long and has a cross section 20 mm^2.

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### 1 Answer

The conductance of a resistor is the inverse of its resistance and is expressed in the units Siemens where x Siemen is equivalent to (1/x) ohm.

In the problem the conductor is a copper wire that is 10 m long and it has a constant cross-sectional area of 20 mm^2.

The conductance C = (A/l)*(1/r), where A is the cross sectional area, l is the length and r is the resistivity. First convert all the values in terms of SI units. Length l = 10 m, area of cross section A = 20 mm^2 = 20*10^-6 m^2 and the resistivity is 1.68*10^-8 ohm*m

C = 20*10^-6/(10*1.68*10^-8)

=> (200/1.68) S

=> 119.04 S

The required conductance of the copper wire is 119.04 S.

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