The force on a current-carrying wire is a maximum when the current is moving parallel to a magnetic field. true or false

The force is given by F=iL×B  where i is current, L is the path the current follows (the wire path) and B is the magnetic field.  Also recall that the × symbol is the vector cross product, which can be expressed by the sine of the angle between the vectors L and B.  Therefore we can also say F=iLBsin(θ).  Do you know what value of θ makes sin(θ) the largest?  This will tell you if parallel or perpendicular makes the force strongest.  For one value of θ it will be zero, and for the other it will be maximized.

The answer is a.  i hope this

Answer(a)   the matererials that are in contact, the two materials and the nature of their surfaces/// (b)/// the force pushing the two surfaces together, pushing the surfaces together causes the more of the asperities to come together and increases the surface area in contact with each other