The device pictured below at the left consists of an alminum cylinder about one inch in diameter and six inches long, extending out from its connection to a motor that rotates at 1725 revolutions per minute (28.75 revolutions per second) when the motor is turned on. The photograph at the right shows a detail of the rod, in which you can see brushes of the type used to transmit current in a generator or motor commutator. One of the brushes touches the center of the cylinder at one end, while the other touches the rod at its center or "equator", midway between the ends. The brush at the end is connected to the positive terminal of a digital voltmeter, and the brush at the equator of the cylinder is connected to the negative terminal of the voltmeter.
When the motor is started, causing the cylinder to rotate rapidly in the clockwise direction when viewed looking from the end of the cylinder back toward the motor:
Click here for Answer #217 after April 18, 2005.
