Question

# A long, hollow, cylindrical conductor (with inner radius 2.0 mm and outer radius 4.0 mm) carries a current of 24 A distributed uniformly across its cross section. A long thin wire that is coaxial with the cylinder carries a current of 24 A in the opposite direction. What is the magnitude of the magnetic field 5.0 mm from the central axis of the wire and cylinder?

Solution

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c) In the last part, we are at the distance $d_3$, outside both the wire and the cylinder. Now we feel the total magnetic field due to the cylinder and the wire together. The cylinder can now be approximated as the wire and similarly to the previous part, we subtract the magnetic fields. But the fields are now equal in magnitude but opposite in direction and annul each other as can be seen in the picture below: