Acharged sphere located at the origin of the xy-plane exerts a force of magnitude f on a charged particle located at (+d, 0). the sphere will exert a force f/2 on the particle if the particle is moved to which of the following locations?

a (+2d, 0)
b (+d, +d)
c (+d/2, 0)
d (0, -d)

explain

Along wire carrying a 4.2 a current perpendicular to the xy-plane intersects the x-axis at x=−1.7cm. a second, parallel wire carrying a 3.0 a current intersects the x-axis at x=+1.7cm. part a at what point on the x-axis is the magnetic field zero if the two currents are in the same direction? express your answer to two significant figures and include the appropriate units.