A Proton Beam That Carries a Total Current of 1

Multiple Choice

A proton beam that carries a total current of 1.3 mA has 10.0 mm diameter. The current density in the proton beam increases linearly with distance from the center. This is expressed mathematically as J(r) = J0 (r/R) , where R is the radius of the beam and J0 is the current density at the edge. Determine the value of J0.

A) 25 A/m²
B) 6.2 A/m²
C) 12 A/m²
D) 17 A/m²