The diagram shows a positive charge moving in a magnetic field.

Question

A field of circles labeled B. There is a positively charged particle with a velocity vector pointing left labeled v.
In which direction is the magnetic force acting on the charge?

into the screen
out of the screen
up
down

Answer 1

To determine the direction of the magnetic force acting on a positive charge moving in a magnetic field, we can use the right-hand rule. Here's how it works:

1. Point your thumb in the direction of the velocity vector (\( \mathbf{v} \)), which, in this case, is to the left.
2. Point your fingers in the direction of the magnetic field (\( \mathbf{B} \)). In the diagram you described, the magnetic field lines are represented by circles, typically indicating a circular magnetic field. Assuming the field lines come out of the screen (which is a common representation when circles are shown), your fingers would point out of the screen.
3. Your palm will then indicate the direction of the magnetic force (\( \mathbf{F} \)) acting on the charge.

Given the setup:

• Velocity \( \mathbf{v} \) is to the left.
• Magnetic field \( \mathbf{B} \) is out of the screen.

Using the right-hand rule, the direction of the magnetic force \( \mathbf{F} \) exerted on the positive charge can be determined to be upward.

Therefore, the magnetic force is acting upward.