Using the right-hand rule, what is the direction of the magnetic field around a straight conductor carrying current upward as viewed from above?

Using the right-hand rule, what is the direction of the magnetic field around a straight conductor carrying current upward as viewed from above?

• A. Clockwise
• B. Counterclockwise
• C. Radial outward
• D. Radial inward

Answer: (B)

The fundamental idea is that the right-hand rule determines the direction of the magnetic field wrapping around a current-carrying wire. For a straight conductor, the magnetic field forms concentric circles around the wire. If you point your right thumb in the direction of the current (upward), the way your fingers curl shows the magnetic field direction. Looking from above, the fingers curl in a counterclockwise sense, so the magnetic field around the wire is counterclockwise when viewed from above. Radial outward or radial inward would imply the field lines point directly away from or toward the wire, which isn’t the case here—the field is tangential, looping around the wire. If the current were reversed, the sense would flip to clockwise.

The fundamental idea is that the right-hand rule determines the direction of the magnetic field wrapping around a current-carrying wire. For a straight conductor, the magnetic field forms concentric circles around the wire. If you point your right thumb in the direction of the current (upward), the way your fingers curl shows the magnetic field direction. Looking from above, the fingers curl in a counterclockwise sense, so the magnetic field around the wire is counterclockwise when viewed from above.

Radial outward or radial inward would imply the field lines point directly away from or toward the wire, which isn’t the case here—the field is tangential, looping around the wire. If the current were reversed, the sense would flip to clockwise.