下列说法中正确的是( )
A:电饭锅工作时,将内能转化为电能
B:电风扇工作时,将机械能转化为电能
C:干电池给灯泡供电时,将电能转化为化学能
D:在阳光照射时,太阳能电池将太阳能转化为电能
阅读下列短文,从每小题的三个选项中选出最佳答案
It is morning now. Look at the sun, it rises in the east(东方). Look at the tree, the shadow is long. It is noon now. The sun is high in the sky. It is very hot. Look at the tree. The shadow is short. It is evening now. The sun goes down in the west(西方). Look at the tree, the shadow is long again. It is night now. The moon is high in the sky. There are some stars in the sky too.
若四位数能被13整除,则两位数的最大值是____ .
物质的溶解速率与多种因素有关.在家中,我们可用____ 方法使白糖快速溶于水,在实验室中,通常要使块状固体快速溶解,除上述方法外,还可以用____ 等方法.
一根弹簧的劲度系数为K=500N/m,竖直悬挂在天花板上,下端有一质量为5Kg的物体(在弹性限度内),处于静止状态,则这时弹簧的伸长量为( )