A charged particle may feel a force due to a magnetic field. The force is zero if the particle is not charged, but are there other conditions for which the force is zero? If so, what are they ?

Estimate the magnetic force felt by an electron moving at 1/10th the speed of light in the magnetic field of the Earth.

If a straight wire carries current parallel to a uniform magnetic field it feels no force. Is it possible to orient a closed loop of current in a uniform magnetic field so that it feels no net force? If so, how?

Estimate the magnetic force felt by a wire in a typical toaster due to the magnetic field of the Earth.