PHYSICS · Multi-part · AP · Physics 2: Algebra-based · Magnetism and Electromagnetism · Magnetism and Electromagnetism
Problem
A small magnetic sensor is placed at Point P, which is located 0.10 m due north of the origin in a horizontal plane. At time t=0, a single ion of unknown charge magnitude |q| moves with constant speed v due east along the +x axis, passing through the origin. Neglect Earth’s magnetic field and all other external fields.
(1) At the instant the ion passes the origin, the sensor at Point P registers a magnetic field directed vertically upward (out of the horizontal plane). Using coordinate relationships, sketch or describe the relative orientation of the velocity vector, the position vector from the ion to Point P, and the magnetic-field direction that would produce this reading.
(2) Using only the information in part (a), determine whether the ion is positively charged or negatively charged. Provide a clear justification for your conclusion.
(3) Immediately after t=0, the ion enters a region that contains a uniform magnetic field that points vertically downward (into the horizontal plane). Determine the direction of the magnetic force that this external field exerts on the ion and justify your answer.
(4) Based on your answer to part (c), predict qualitatively the subsequent path (curving toward north, south, up, or down relative to the plane) that the ion will follow while in the uniform magnetic field region. Explain your reasoning in terms of the directions of velocity and force.