A thin shell(薄壳) of radius r and thickness dr is shown shaded.
举一反三
- the ratio between the thickness of the bold line and the thin line is .
- The basic line thickness of the drawing refers to the thickness for the ( ) line A: thin B: semi-bold C: bold D: middle
- The cap and new shell are tightened up and then removed and the thickness of the wire measured by （）.
- The ratio between the thickness of the thin line and the bold line is A: 4 B: 2 C: 0.5 D: 0.25
- 一半径为R的薄金属球壳,带电量q,壳外真空,壳内充满相对介电常数为εr的各向同性均匀电介质.设无穷远处为电势零点,则球壳的电势V= .