What current flows through a 2.62 cm diameter rod of pure silicon that is 23.5 cm long, when 1000 v is applied to it? (such a rod may be used to make nuclear particle detectors, for example.) the resistivity of pure silicon is 2.30 103 ω · m?

Resistivity = resistance * Area / Length
resistance = ??
rho = 2.30 * 10^3 ohms meters.
l = 23.5 cm = 0.235 meters.
diameter = 2.62 cm = 0.0262 m
Radius = diameter / 2 = 0.0131 m
Area = pi r^2 where pi = 3.14
Area = 3.14 * 0.0131^2 = 0.000539 m^2

2.30 * 10^3 = R * 0.000539 /0.235
2.30 * 10^3 * 0.235/0.000539 = R
R = 1002783 which is about 1 meg ohm, but I'll use the calculation here.

E = 1000 V
R = 1 002 783 ohms
I = ???

E = I * R
1000 = I * 1002783 We should really round that resistor to 1 megohm or 1 * 10^6 ohms.

I = 1*10^3 / 1 * 10^6
I = 1 * 10^-3 amp = 1 milliamp. Pretty reasonable all things considered. 

The radiation of the fire causes the saucepan to heat up. the conduction of the saucepan then to distribute the heat over the saucepan and to give heat to the water. the convection of the water distributing the heat within the water, till all the water is boiling