The magnetic field around a long straight current carrying wire consists of
Correct answer: B. concentric circles centred on the wire
- A. straight lines parallel to the wire
- B. concentric circles centred on the wire
- C. lines radiating outwards from the wire
- D. no field at all
Explanation
The right hand grip rule gives the sense of the circles: point the thumb along the conventional current and the curled fingers show the field direction. The strength falls off as one over the distance from the wire, not as one over the distance squared. Inside a long solenoid, by contrast, the field is nearly uniform and parallel to the axis.
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About Magnetic Flux Density
Magnetic flux density measures the magnetic force acting on a current carrying conductor or moving charge in a magnetic field. Work includes the relations B equals F divided by IL and F equals qvB, the tesla as its SI unit, field direction and the distinction between flux density and magnetic flux.
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