How are magnet fields and electric fields alike?

Both act only on charged particles (ions, protons, or electrons). ?However, an electric field (which generates an ELECTRIC FORCE) acts on a particle in the same direction as the field, given by the equation:

F(vector) = q*E(vector)

The resulting force vector is in the same direction as the field vector (for positive charges).

A magnetic field generates a force ONLY on a MOVING charge, and ONLY if the charge is moving non-parallel to the magnetic field:

F(vector) = q*v(vector) x B(vector)

Because of the cross-product, the magnetic force is a direction perpendicular to the velocity and magnetic field vectors (use the right hand rule to figure out the direction of magnetic force). ?The particle will still have momentum from its initial velocity, so an applied magnetic field will (pretty much) always make the particle move in a curved path.