Two equal-magnitude forces are applied to a door at the doorknob. the first force is applied perpendicular to the door, and the second force is applied at 30° to the plane of the door. which force exerts the greater torque about the door hinge?

in first case the torque is maximum.

Explanation:

Torque is defined as the product of force and the perpendicular distance.

τ = F x d x Sinθ

In case A: the angle between force vector and the distance vector is 90 so torque is

τ = F x d

In case B: the angle between force vector and the distance is 30°.

τ = F x d x Sin30

τ = 0.5 Fd

So the torque is maximum in first case.

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.