# Induced Charge 5A40.13

Electrometer and Faraday Cage located in Electrostatics Cabinet, B1.

1000V DC Power Supply located in Electrostatics Cabinet, B2.

Large, adjustable parallel-plate capacitor located in Electrostatics Cabinet, A4.

Proof planes located in Electrostatics Cabinet, A1.

Connect the electrometer to the Faraday Cage, so that the outside cage is grounded. Set the electrometer so that the center measures 0V.

Connect a short alligator-clip lead to the outside cage, so that the inside cage can be grounded if necessary.

Connect the 1000V DC Power Supply to the parallel-plate capacitor, and set the capacitor plates about 5 cm apart. Note which side of the capacitor charges positive.

Touch the outside of the Faraday Cage with both hands to remove any charge you may have on your hands; then in turn touch each proof plane and each proof plane handle to the outside cage.

Insert each proof plane into the inner Faraday Cage. The needle on the electrometer should not move.

Place the proof planes on top of each other (flat side to flat side) and insert them together into the Faraday Cage. The needle on the electrometer should not move.

Keep the proof planes on top of each other and insert them in between the plates of the capacitor, so that the proof planes are parallel to the capacitor plates. Carefully separate them, and remove them without touching each other or the capacitor plates.

Insert the proof planes one at a time into the inner Faraday Cage. One of them should now show a positive charge (the proof plane that was closest to the grounded plate of the capacitor) and one should now show a negative charge of equal magnitude (the proof plane that was closest to the positive terminal of the capacitor).

Discussion: The field in the capacitor causes one charges to redistribute themselves in the proof planes so that the field in the conducting metal of the proof planes is zero. This means one plane charges positive and one negative.