A particle of charge moves in a circle of radius in a uniform magnetic field

PHYSICS · Subjective · A Level · Physics · Fields and their consequences · Fields and their consequences

Problem

A particle of charge

q

moves in a circle of radius

10\,\text{cm}

in a uniform magnetic field

B

. Its kinetic energy is increased from

2.0\,\text{MeV}

8.0\,\text{MeV}

, but the radius of the path must remain the same. By what factor should the magnetic field be changed?