Explain why two ebonite rods, both charged with fur repel

Two ebonite rods rubbed with fur will have similar negative charges and like charges repel each other. Hence, the two rods will repel each other.

Explanation:

When an ebonite rod is rubbed with fur, fur loses electrons and ebonite rod gains electrons. fur becomes positively charged and rod becomes negatively charged.

the minimum amperage that the current in this wire would have to have so that its weight is completely supported by the magnetic force due to earth's field, assuming that no other forces except gravity act on it

see the picture for the vector

the magnitude of the vector by pythagorean theorem

r = √( (-10)^2 + (3)^2 ) = √109

magnitude = √109 units

the direction angle between vector and x-axis is

tan^(-1)(3/10) = 16.699

so the direction is approximately 16.7 degrees north of west