For this reason, the coil can turn only until the motion caused by the current is balanced by the twist of the suspending wire. 伯莎M.克拉克.科学通论.
But as the coil turns, the suspending wire becomes twisted and hinders the turning. 伯莎M.克拉克.科学通论.
The balance can be regained by suspending an equivalent weight at the opposite end of the bar, or by applying a 2-pound weight at a point 3 inches to the left of _F_. 伯莎M.克拉克.科学通论.
It is easy to see that long-continued rotation would be impossible in the arrangement of Figure 228, since the twisting of the suspending wire would interfere with free motion. 伯莎M.克拉克.科学通论.
A very striking experiment can be made by suspending from the ceiling a heavy weight and striking this weight gently at regular, properly timed intervals with a small cork hammer. 伯莎M.克拉克.科学通论.