A rod of a certain metal is 1.0 m long and 0.6 cm in diameter. Its resistance is `3.0 times 10^-3 Omega` . Another disc made of the same metal is 2.0 cm in diameter and 1.0 mm thick. What is the resistance between the round faces of the disc?

Options

A. `1.35xx10^(-6)Omega`
B. `2.7xx10^(-9)Omega`
C. `4.05xx10^(-6)Omega`
D. `8.1xx10^(-6)Omega`

Answer

B

Explanation

By using R=`p(l)/(A)`,`(R_(disc))/(I_(rod))xx(A_(rad))/(A_(disc))` `rArr` `(R_(disc))/(3xx10^(-3))`=`(10^(-3))/(1)xx(pi(0.3xx10^(-2)))/(pi(10^(-2))^(2))` `rArr` `R_(disc)`=`2.7xx10^(-70Omega)`