# Magnetism AP Free Response Problem, HELP!

1. Feb 4, 2010

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1. The problem statement, all variables and given/known data
teacherweb.com/CT/TrumbullHS/.../APOralFinalQuestions1-10.doc for pic.

The magnitude of the magnetic field in teslas at a distance d from a long straight wire carrying a current I is given by the relation B = 2 X 10-7 I/d. The two long straight wires shown above are perpendicular, insulated from each other, and small enough so that they may be considered to be in the same plane. The wires are not free to move. Point P, in the same plane as the wires, is 0.5 meter from the wire carrying a current of 1 ampere and is 1.0 meter from the wire carrying a current of 3 amperes.

a. What is the direction of the net magnetic field at P due to the currents?

b. Determine the magnitude of the net magnetic field at P due to the currents.
A charged particle at point P that is instantaneously moving with a velocity of 106 meters per second toward the top of the page experiences a force of 10-7 newtons to the left due to the two currents.

c. State whether the charge on the particle is positive or negative.

d. Determine the magnitude of the charge on the particle.

e. Determine the magnitude and direction of an electric field also at point P that would make the net force on this moving charge equal to zero.

2. Relevant equations

B = mu not * current / 2 pi r

F = B I L

3. The attempt at a solution

For part b) i found the net magnetic field as 2.0 times 10 ^ 7, is this right? and I don't know how to do anything elsee! please help