Answer: concentric circles.
- A concentric circles
- B straight parallel lines
- C closed square loops
- D no regular pattern
Correct answer: A. concentric circles
Explanation: The field lines are concentric circles centred on the wire.
The magnetic field around a long straight current-carrying wire forms concentric circles, with direction given by the right-hand rule (point thumb along I, fingers curl in the direction of B).
Concept context
Magnetic force on moving charges and currents, the Biot-Savart law, Ampere's law, and the cyclotron - how electric currents create and respond to magnetic fields.