Example 1 · difficulty 3/5
A steady current I flows uniformly through the cross-section of a long cylindrical wire of radius R. The ratio of the magnetic field at a point inside the wire at a distance R/2 from the axis to the field at a point outside the wire at a distance 2R from the axis is:
- A. 1 : 1
- B. 1 : 2
- C. 1 : 4
- D. 2 : 1