To understand the forces between a bar magnet and 1. a stationary charge, 2. a moving charge, and 3. a ferromagnetic object. A bar magnet oriented along the y axis can rotate about an axis parallel to the z axis. Its north pole initially points along j^.

Explanation:

1. If the charge is stationary and it is not moving, then the magnetic force will be zero, since the velocity is 0m/s

From the formula of magnetic force

F = q(V×B)

And since V is 0, then, the magnetic force is zero

F = 0N,

No torque at all.

2. The moving charge interacts with the fixed magnet. The force between them is at a maximum when the velocity of the charge is perpendicular to the magnetic field.

From the formula of magnetic force

F = q( V×B)

V × B = |V|•|B| Sinθ

So, Sinθ has its highest value at 90° in the range of 0-360°

So, the force will have a maximum value when the moving charge is perpendicular to the magnetic field

Now, since the magnetic field is in the positive y-direction, for the force to be maximum the electron must move the positive x-direction.

So the force will be in the positive z-direction(since i×j= k).

3. Now, the charge is replaced by an electrically neutral piece of initially unmagnetized soft iron (e.g. nail) that is not moving. This result into the magnetic experience a force due to the iron fillings attracting its north pole.

0.19 m/s and 0.45 m/s

does anyone know or what?