By using a pole-changer to cycle the electromagnet's polarity, Henry caused the permanent magnet to tap a small office bell.
(Henry; caused; the permanent magnet to tap a small office bell; T:By using a pole-changer to cycle the electromagnet's polarity) Context(Henry caused,List([63, 75))):(the permanent magnet; to tap; a small office bell)
Henry caused,List([63, 75))
Henry the permanent magnet
caused to tap
the permanent magnet to tap a small office bell T:By using a pole-changer to cycle the electromagnet's polarity
a small office bell