Consider the mass spectrometer shown schematically in Figure 29.23. The electric field between the plates of the velocity selector is 2 500 V/m, and the magnetic field in both the velocity selector and the deflection chamber has a magnitude of 0.035 0 T. Calculate the radius of the path for a singly charged ion having a mass m = 2.18 times 10-26 kg. Figure 29.23 A mass spectrometer. Positively charged particles are sent first through a velocity selector and then into a region where the magnetic field B0 causes the particles to move in a semicircular path and strike a photographic film at P.
Explanation / Answer
speed of ion = E / B = 2500 /0.0350 = 71429 . Then... . centrip force = magneticforce . mv2 / r = qvB . r = mv / qB = 2.18x 10-26 * 71429 / 1.60 x 10-19 *0.035 = 0.278 m = 27.8cm