physics, university
posted by Stacey .
A length of wire has a radius of 3.00 x 103 m and a resistance of 0.200 ohms. When the potential
difference across the wire is 10.0 volts, the electron drift speed is found to be 2.98 x104 m/s. On the
basis of these data, calculate the density of free electrons in the wire.

J=nev,
where
J is the current density,
n is free electron density,
e=1.6•10⁻¹⁹C ,
drift velocity v= 2.98•10⁻⁴ m/s
J=U/RA,
where
U=10 V,
R=0.2 Ω,
A= πr²
n•e•v= U/R•π•r²
n= U/R•π•r²• e•v=...