A small plastic bead of mass m carries a positive charge +q. It hangs motionless in a uniform upward electric field E that exactly balances its weight. The electric field is then instantaneously doubled in magnitude while its direction remains upward. Which of the following describes the bead’s subsequent motion?
a) It accelerates upward with magnitude 2g.
b) It accelerates upward with magnitude g.
c) It remains at rest.
d) It accelerates downward with magnitude g.