a 130 v battery is connected across two parallel metal plates of area 28.5 cm2 and separation 8.50 mm. a beam of alpha particles (charge 2e, mass 6.64×10−27kg) is accelerated from rest through a potential difference of 1.75 kv and enters the region between the plates perpendicular to the electric field. part a what magnitude of magnetic field is needed so that the alpha particles emerge undeflected from between the plates?
