A Proton Cyclotron Has a Magnetic Field of 0

A proton cyclotron has a magnetic field of 0.20 T between its poles and a radius of 0.40 m. What is the maximum energy for the protons from this machine?

A) 1.6 × 10⁻¹³ J
B) 3.2 × 10⁻¹³ J
C) 4.9 × 10⁻¹³ J
D) 3.2 × 10⁻¹⁴ J
E) 4.9 × 10⁻¹⁴ J