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JAMB Physics 1988 Question 37

Question 37

Magnetism

The wire X in the figure above is at right angles to the plane of the paper and carries a current into the paper. At which of the points labelled 1 - 4 will the magnetic flux density due to this current be in the same direction as that of the horizontal component of the earth's magnetic field?

Diagram for this question
  1. A.1
  2. B.2
  3. C.3
  4. D.4
Show the answer and explanation

Answer: C (3)

Explanation

A current into the paper makes clockwise field lines. Going clockwise, the field at point 3 (to the left of the wire) points up the page, towards magnetic north, like the earth's horizontal field.