A velocity selector in a mass spectrometer uses an electric field of 4.4 x 105 V/m. What magnetic field strength (in Tesla) is needed to select a speed of 4.8 x 106 m/s

B = 9.16 10⁻² T

Explanation:

The speed selector is a configuration where the electric and magnetic force has the opposite direction, which for a specific speed cancel

q v B = q E

v = E / B

B = E / v

Let's calculate

B = 4.4 10⁵ / 4.8 10⁶

B = 9.16 10⁻² T