A research team studies tiny dust grains that carry an unknown electric charge
PHYSICS · Multi-part · AP · Physics 2: Algebra-based · Magnetism and Electromagnetism · Magnetism and Electromagnetism
Problem
A research team studies tiny dust grains that carry an unknown electric charge q. Each grain is shot at a speed of 2.8×104m/s into a uniform magnetic field of magnitude 0.050T. The velocity of the grains is perpendicular to the magnetic field, and sensors attached to a calibrated micro-spring show that each grain experiences a magnetic force of 1.12×10−15N.
(a) Determine the magnitude of the electric charge q on a dust grain.
(b) The researchers reverse the direction of the magnetic field while keeping its magnitude unchanged. Describe both the magnitude and the direction of the magnetic force that will now act on a dust grain, and explain your reasoning.
(c) In a follow-up test, the field magnitude is doubled (with its direction restored to its original orientation). Predict the new magnetic force acting on a grain and explain how this result supports or refutes the direct proportionality between magnetic force and magnetic field strength.