PHYSICS · Multi-part · AP · Physics 2: Algebra-based · Magnetism and Electromagnetism · Magnetism and Electromagnetism
Problem
In a laboratory device, a uniform electric field is directed upward between two parallel plates that are 4.0cm apart. A uniform magnetic field fills the same space. Both fields are initially adjusted so that a beam of singly ionized neon ions (charge +e, mass 3.3×10−26kg) entering horizontally from the left passes straight through the region without deflection.
(1) Part 1: Describe qualitatively the condition that must hold between the electric and magnetic forces for the ions to pass through undeflected.
(2) Part 2: The experimenter doubles only the electric field strength while keeping the magnetic field unchanged. Explain the subsequent path the ions will follow and justify your answer in terms of the relative magnitudes and directions of the forces.
(3) Part 3: Next, the magnetic field is turned off entirely while the doubled electric field remains. Predict and explain how both the speed and direction of motion of the ions will change as they traverse the region between the plates.
(4) Part 4: Finally, suppose the original electric field (before doubling) is restored and the ions are replaced by electrons that have the same initial speed as the ions and enter along the same horizontal line. Discuss, with reasoning, whether the electrons will emerge undeflected, be deflected upward, or be deflected downward.