在如图所示的杠杆中,O是__________,若F1是动力,则F2是__________,动力臂是__________,阻力臂是__________。
支点,阻力,OB,OA
As a student of Senior Three, he has very little free time __ he can spend developing his own interest.
A.when
B.in which
C.at which
D.that
如图所示,LC振荡回路中振荡电流的周期为2×10-2 s,自振荡电流沿逆时针方向达最大值时开始计时,当t=3.4×10-2 s时,电容器正处于________(填“充电”“放电”“充电完毕”或“放电完毕”)状态.这时电容器的上极板________(填“带正电”“带负电”或“不带电”).