Which statement describes an example of static electricity? O A. A person rubs a shoe on a rug, causing extra electrons to be
transferred to the shoe.
O B. Electric charges move from a position of higher potential energy
to a position of lower potential energy.
O C. Electrons flow from an outlet into a toaster, causing it to heat a
slice of bread.
O D. A conductor allows electrons to flow through it.

Cyclotrons are widely used in nuclear medicine for producing short-lived radioactive isotopes. these cyclotrons typically accelerate h- (the hydride ion, which has one proton and two electrons) to an energy of 5 mev to 20 mev. this ion has a mass very close to that of a proton because the electron mass is negligible—about 1 2000 of the proton’s mass. a typical magnetic field in such cyclotrons is 1.9 t. (a) what is the speed of a 5.0-mev h-? (b) if the h- has energy 5.0 mev and b = 1.9 t, what is the radius of this ion’s circular orbit?