The resistivity of copper is 1.7 X 1O^-8 ohm m. What length of copper wire of diameter 0.1 mm will have a resistance of 34 ohm?

1 Answer
Apr 29, 2018

Resistance #R# of a conducting wire of length #l# and of area of cross section #A# is given by the expression

#R=rhol/A#
where #rho# is resistivity or specific resistance of the material of the conductor.

Inserting given values in the expression in SI units we get

#34=(1.7 xx 10^-8)l/(pi(0.1/(1000))^2/4)#
#=>l=34/(1.7 xx cancel(10^-8))xxpi/4cancel((0.1/(1000))^2)#
#=>l=15.71\ m#, rounded to two decimal places.