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Question
State the two properties of the magnetic lines of force around a circular coil.
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Solution
The important properties are:
(i) The magnetic lines of force near the wire are nearly circular, especially at the points where
the current enters or leaves the coil.
(ii) At the centre of the coil, the lines of force are almost parallel to each other, showing that the magnetic field at the centre or the coil may be considered uniform.
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(i) A straight wire conductor passes vertically through a piece of cardboard sprinkled with iron filings. Copy the diagram and show the setting of iron filings when a current is passed through the wire in the upward direction and the cardboard is tapped gently. Draw arrows to represent the direction of the magnetic field lines.

(ii) Name the law which helped you to find the direction of the magnetic field lines.
