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Shown below in the photograph at the left and in the detail at the right is a device called a Faraday cage. In the detail photograph three suspensions of aluminum foil chunks on pieces of string can be seen. Each of the suspensions include a string passing over the top of the cylindrical screen with small rectangular chunks of aluminum foil, a few centimeters in size, attached to the ends of the string. Note that one end of each string is outside the cylinder and one end of the string is inside the cylinder.
What do the foils do when the van de Graaff generator is turned on, putting large negative charge onto the cylindrical screen and perhaps by conduction onto the foils. In particular, when the cylinder is charged, which, if any, of the aluminum foils will move away from the cylinder, either inward or outward.
When the cylinder is charged:
(1) only the inner foils will move away from the cylinder.
(2) only the outer foils will move away from the cylinder.
(3) both the inner and the outer foils will move away from the cylinder.
(4) neither the inner nor the outer foils will move away from the cylinder.
Shown below is an unusual Faraday cage constructed from two sieves. An electroscope is attached to the sieve at the rear, as seen in the photographs at the center and the right. These photographs were taken with no charge on the system.
Now the van de Graaff generator is turned on for a few seconds, charging the Faraday cage system. The electroscope continues to indicate no charge - it remains in its upright position, as seen in the center photograph.
When the sieves are separated, as seen in the photograph at the right, but with the system charged, what will happen?
(1) The electroscope will indicate charge.
(2) The electroscope will stay as it is.
(3) Something else will happen (specify what).
A radio is tuned to Washington, DC, SportsTalk 980 when it is suddenly and for no apparent reason covered by the wire mesh seen in the photograph below.
What happens to the sound of the radio after the wire mesh is in place.
After placing the wire mesh on the radio, the radio will:
(1) be louder.
(2) be softer.
(3) remain at about the same volume.
Millikan Oil Drop Experiment
Pictures courtesy of Clarkson University
Photo Courtesy of American Museum of Science and Energy
Photo Courtesy of Jefferson Lab