Electric Current?

Question

A cylindrically shaped beam of protons has a diameter of 2.00mm and has 1.20 x10^6 protons per cubic cm. The kinetic energy of each proton is 1.00 keV.

a) what is the speed of each proton in the beam?

b) what is the beam current in amperes?

Answer 1

A. m(proton) = 1.672622E-27 kg

KE = 1000 eV * 1.602177E-19 J/eV = 1.602177E-16 J

v = sqrt(2KE/m) = 437695 m/s

B. To solve for current, determine the volume V (in cc) of the beam of length 437695 m. This the beam volume passing a given point in 1 second. Multiply V by protons/cc and by 1.602177E-19 unit charges/coulomb.