7. A) In the e/m experiment we did in our lab, an electron starting from rest travels through a potential difference of 280 V and then moves into a uniform magnetic field that varies with current / according to B(/) = (7.9 x 10 *7/A) /. Find the radius of the electron's orbit when the current is 2.0A. B) In Figure 8, a charged particle of charge q - -2.5 x 10-6 C and mass m - 3.4 x 10-12 kg has velocity vo - 9.2 x 105 m/s as it enters a region of uniform magnetic field. The particle is observed to travel in the semicircular path with radius R - 6.0 cm. What is the magnitude and direction of the magnetic field in the region? Region of magnetic field R Path of VO the particle Figure 8