不可以作为档案载体使用的材料有()。
A.无酸纸
B.复印纸
C.传真纸
参考答案:B, C
如图所示,在匀强电场中有a、b、c三点,a、b相距4 cm,b、c相距10 cm.将一个带电荷量为2×10-8 C 的电荷从a点移到b点时,电场力做功为4×10-6 J.将此电荷从b点移到c点时电场力做功为________ J,a、c间电势差为________V.
For small angles of inclination,if the KG were equal to the KM,then the vessel would have().
A.positive stability
B.negative stability
C.neutral stability
D.maximum stability