As seen, any object with electric charge, stationary or moving, other than the charged object that created the field, experiences a force in an electric field. Also, any object with electric charge, stationary or moving, can create an electric field. Similarly, an electric current or a moving electric charge, other than the current or charge that created the field, experiences a force in a magnetic field, and an electric current created a magnetic field.

a. To understand how a moving charge can also create a magnetic field, consider a particle with charge q moving with velocity v. Define the position vector r = r. r leading from the particle to some location. Show that the magnetic field at that location is

B= µo/4π= qv x r/r^2

b. Find the magnitude of the magnetic field 1.05 mm to the side of a proton moving at 1.50 x 10^7 m/s.
c. Find the magnetic force on a second proton at this point, moving with the same speed in the opposite direction.
d. Find the electric force on the second proton