Answer to Question #175357 in Physics for aria

Question

jose wants to use a glass rod as an insulator. the rods diameter is 9 mm and kts resistivity is 1×10^9m. how long must be the rod to he offer a resistance of 9.1×10^10 ohms?

Answer 1

$R=\rho \frac{l}{A}\to l=\frac{RA}{\rho}$

$A=\pi d^2/4=3.14\cdot0.009^2/4=6.36\cdot10^{-5}\ (m^2)$

$l=\frac{RA}{\rho}=\frac{9.1\cdot10^{10}\cdot 6.36\cdot 10^{-5}}{1\cdot10^9}\approx0.006\ (m^2)=6\ (mm)$ . Answer