A charged particle moves through space with constant velocity (magnitude and direction). If the external magentic field is zero in this region, you can conclude that the external electric field in this region is also zero.
In a different scenario, if the external E-field is zero, can you conclude that the external B-field is also zero? Explain in 100 words or less.
* In both cases, consider that there are no other fields or forces other than possible electric and magnetic forces. Ignore the E and B fields created by the moving charged particle as these fields do not affect the particle that created them