A magnetic field of magnitude B 55 times 103 T is confined

A magnetic field of magnitude B = 5.5 times 10^-3 T is confined to a region 10 cm wide and is directed into the page. A particle of charge q = 3.2 times 10^-19 C and mass m = C.C times 10^-27 kg is traveling horizontally to the right (in the plane of the page) with a speed v = 5.0 times 10^6 m/s when it enters the magnetic field. (a) The particle will execute a circular path of what radius inside the field? (b) Suppose we want the particle to pass through the magnetic field undetected. An electric field of what magnitude and direction could accomplish this?

Solution

a) qvB=mv^2/r so r = mv/qB = 6.6 * 10^-27 * 5*10^6/3.2*10^-19*5.5 * 10^-3 = 18.75 m

b) if E is elctrcif field then qE = qvB

so E = vB = 5*10^6*5.5 * 10^-3 = 2.75 * 10^4 N/m opposte to direction of motion