Suppose that the magnetic field in some region has the form b = kz ˆx (where k is a constant). find the force on a square loop (side a), lying in the yz plane and centered at the origin, if it carries a current i , flowing counterclockwise, when you look down the x axis.

Explanation:

As we know that loop is placed in YZ plane and magnetic field is along x direction

So here net force on the side of the loop which lies along Y axis is given as

here we know that on Y axis z = 0

so B = 0

so we have

now on the opposite side we have z = a

so magnetic field is given as

so force on that side is given as

so net force on the loop is given as

there are no contact forces mentioned on the list of choices that you've provided.