If a magnetic field is to exert a force on a current-carrying wire, the field must have some vector component:
a) parallel with the current
b) tangential to the current
c) concentric with the current
d) perpendicular to the current

Which of the following correctly describes what happens when an atomic bomb explodes? small pieces of fissionable material are joined and form a body with a mass greater than the critical mass, the relative number of neutrons escaping decreases, and a chain reaction and explosion result. large pieces of fissionable matter are brought together quickly and form a body with a mass smaller than the critical mass, the relative number of escaping neutrons increases, and a chain reaction and explosion result.