Finite Arc

Center of a Closed Loop (q = 2 p)

Axis of a Closed Loop (Distance d from the center)

Axis of a long Solenoid (n turns per unit length)

• The direction of the B-field is perpendicular to the plane of the loop(s) or arc
• For an ideal solenoid of infinite length the B-field is constant through out the interior of the solenoid and zero outside the interior of the solenoid.
• One difference between a solenoid with N turns and a loop of N turns is that a loop is nearly flat were as a solenoid is N planer loops side-by-side in a helical winding.

Modified right hand rule for Loops:
Curl your fingers along the direction of the current around the loop(s), your thumb will point along the direction of the B-field

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