Aflat coil is in a uniform magnetic field. the magnetic flux through the coil is greatest when the plane of its area is

perpendicular to the magnetic field

Explanation:from magnetic flux = qvbcos∆

At perpendicularity ∆ is 0 there by making cos 0 = 1

Magnetic flux = qvb

pythagoras' theorem

square root (-5^2+9^2)

square root (25+81)

square root (106)

angle is tan^-1(9/5)

neg x, pos y

the answer is the first electromagnet (a). this is because it has more coils around the ferromagnetic material. increasing the number of coils increases the surface area in which the metal interacts with the current in the coil. this enables more atoms in the metal to become aligned hence becoming more magnetized.