Question

the diagram provided shows a long, straight wire carrying current i within a region of uniform magnetic field. the magnetic force experienced by the wire is also indicated in the diagram, but the magnetic fields direction is not shown. given the information in the diagram, what must the direction of the magnetic field be?
○ out of the plane of the figure
○ upward
○ no magnetic force is exerted on the wire
○ into the plane of the figure
○ downward

Explanation:

Step1: Recall the right - hand rule

The magnetic force on a current - carrying wire is given by $\vec{F}=I\vec{L}\times\vec{B}$, where $I$ is the current, $\vec{L}$ is the length vector of the wire in the direction of the current, and $\vec{B}$ is the magnetic field. The direction of the cross - product $\vec{L}\times\vec{B}$ can be found using the right - hand rule.

Step2: Apply the right - hand rule

Point the fingers of your right hand in the direction of the current ($\vec{L}$). Curl your fingers towards the magnetic field ($\vec{B}$). Your thumb will point in the direction of the magnetic force ($\vec{F}$). Given the current direction (downward) and the force direction (left - hand side as shown), when we apply the right - hand rule, if we point our fingers down (direction of current) and our thumb to the left (direction of force), then our curled fingers will indicate that the magnetic field is out of the plane of the figure.

Answer:

out of the plane of the figure