如图所示,线圈面积为S,电阻为R,求线圈由图示位置转过60°角的过程中,通过线圈某一横截面的电荷量.
因为电动势平均值
而ΔΦ=Φ2-Φ1=BSsin60°= BS
平均电流
They ____ on (集中精力于) keeping their soil rich and free of disease.
图文配对。
① ____ A. It's cloudy.
② ____ B. It's rainy.
③ ____ C. I like eating apples.