Question

Which of the following correctly describes the magnetic field lines near a long straight wire?

• A. The field consists of straight lines perpendicular to the wire
• B. The field consists of straight lines parallel to the wire
• C. The field consists of radial lines originating from the wire
• D. The field consists of concentric circles centred on the wire

Answer 1

The correct option is D

The field consists of concentric circles centred on the wire

The magnetic field lines near a long straight wire are concentric circles with centre at the axis of the conductor (as shown in the figure below) and the direction of field lines can be found using right-hand rule. When a straight current-carrying conductor is clasped in such a way that the thumb points in the direction of the current, the direction in which the fingers wrap is the direction of the magnetic field around the conductor.