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a=5 b=4 m=75 n=30 A long straight wire carries a current of (m/2) A to the North

ID: 2062287 • Letter: A

Question

a=5 b=4 m=75 n=30

A long straight wire carries a current of (m/2) A to the North. A circular loop of wire in the horizontal plane has a radius of radius (a) cm, and carries a current of (n/2) A. If (n) is even, then this current is clockwise, as seen from above; if (n) is odd, then this current is counterclockwise. Point P is at the center of the loop, (a+b) cm from the straight wire.
(a) What is the magnetic field (magnitude and direction) due to the wire, at point P?
(b) What is the magnetic field (magnitude and direction) due to the loop, at point P?
Note: a “loop” is a coil with just one turn.

Explanation / Answer

By the right hand rule of magnetic fields, direction of electric field is along your fingers when your thumb is pointing along direction of current, it also means E.F is always perpendicular to direction of current. E.F for wire is calculated by B = 2*e-7*I/r, where I=current in amperes, r = distance in meters. E.F for loop is calculated by B = pi*2*e-7*I/r , where I=current in amperes, r = distance in meters.