What is the magnitude of the magnetic field?

Question

An alpha particle (the nucleus of a helium atom, carrying a charge of 3.2 £ -19 C moves at 1.2 £ 7 m/s at a right angle to

a magnetic field. The charge on a proton is 3.2 £ -19 C.

If the particle experiences a force of 3.8 £ -14 N due to the magnetic field, what is the magnitude of the magnetic field? Answer in units of T.

Answer 1

The Lorentz force on a charged particle is given by F = qvB. Solve for the magnetic field.

B = F / qv

= (3.8 x 10^-14 N) / ((3.2 x 10^-19 C) x (1.2 x 10^7 m/s))

= 9.9 x 10^-3 T