A2L Item 196
- Description: Indicate the situation in which a moving charge in a magnetic field travels the greatest distance.
- Goal: Reasoning with magnetic forces
- Source: UMPERG-283-625
- Keywords: Displacement, Electromagnetism, Magnetic Field, Right-Hand Rule
The question for students:
In the following situations a charge q moves in a uniform magnetic field. The strength of the magnetic field is indicated by the density of field lines. In all cases the speed of the charge is the same. For which situation(s) will the charge q travel the greatest distance in a given time T?
- 1
- 2
- 3
- 4
- 5
- 1 & 3
- 2 & 4
- 1, 2, 3 & 4
- 1, 2, 3, 4 & 5
- Cannot be determined
Commentary for teachers:
Answer
(9) The magnetic force can change the direction of the velocity but not the speed. The distance traveled, therefore, cannot depend upon either the strength or orientation of the magnetic field. It is important to have students who pick one of the other choices verbalize their reasons. Some students may interpret the question as asking for the ‘displacement’ and, thinking that the time is needed, respond #10. Actually the result for displacement is #5.