A．元电荷就是质子
B．物体所带的电量只能是元电荷的整数倍
C．元电荷是带电物体电量的最小值
D．由库仑定律F=k 可知，当两电荷间距离r→0时，F→∞
BC
Many social workers went to Ya’an to help clean water and food to local people to reduce their pain from the earthquake.
A．put out
B．come out
C．work out
D．give out
软组织摄影用X线管阳极的靶面材料是
A．钨
B．铁
C．金
D．铝
E．钼
可知，当两电荷间距离r→0时，F→∞