Why are electromagnets used in metal scrap yards? They are temporary magnets, so they can be turned on and off.

They are temporary magnets, so eventually the metal just falls off.

They are weak permanent magnets.

They are very powerful permanent magnets.

An electron and a proton have the same kinetic energy upon entering a region of constant magnetic field and their velocity vectors are perpendicular to the magnetic field. suppose the magnetic field is strong enough to allow the particles to circle in the field. note: you'll need to look up the masses for an electron and proton. 1) what is the ratio of the radii of their circular paths rp/re?

An electron is traveling with initial kinetic energy k in a uniform electric field. the electron comes to rest momentarily after traveling a distance d. (a) what is the magnitude of the electric field

What are the north and south poles of a solenoid change with?