eisco PH0917A Demonstration Electroscope Instruction Manual
- June 1, 2024
- eisco
Table of Contents
Demonstration Electroscope
PH0917A
Instruction Manual
Demonstration Electroscope
Introduction:
The primary purpose of the apparatus is to detect the presence of and measure the magnitude of a static electric charge. A charge is either induced or conducted through the metal plate on the top of the device. The electroscope needle attached to the central rod deflects due to the charge induced on the metal plate.
Kit contents:
– Needle Electroscope Apparatus
– Metal conductor sphere
– Metal conductor plate
– Metal charging plate on insulating rod
Required components not included:
– Charge producing device (such as a balloon, or a plastic rod and a wool
cloth
– 4mm banana plug cord (optional)
Procedure
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Attach a metal conductor to the top of the electroscope apparatus (either the sphere or the plate).
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Produce an electrostatic charge. Example methods include rubbing an inflated balloon on one’s head, or rubbing a plastic rod with a wool cloth.
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(Optional) If desired, one can transfer this charge via conduction (touching it) to the metal plate attached to the insulating rod.
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Induction: Bring the charged balloon or rod near the conducting plate atop the electroscope. When the negatively charged object gets near the plate (but not touching) a charge will be induced along the metal support bar and electroscope needle. The similar charges along the support and needle will cause a repulsive force and the needle will deflect. The amount of deflection corresponds to the amount of charge on the charged object, as well as the distance from the charged object to the conducting plate or sphere. See the figure below for a depiction of the charge migration.
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With the charged object still in proximity to the conducting sphere, ground the support bar. To do so, one can connect a 4mm banana plug cord to the red grounding terminal under the ring and touch the support bar with the opposite lead. The needle should return to the vertical position.
Alternatively in the absence of a 4mm banana plug cord, one can ground the electroscope by touching the support bar with a finger.
Having grounded the support bar, move the charged object away from the conducting plate. The electroscope will now have a net positive charge, as the negative charges moved to ground. The needle should deflect again and stay deflected. -
Conduction: Alternatively one can charge the electroscope via conduction instead of induction. In this case, touch the charged object to the conducting plate, and the charge will transfer over to the electroscope, causing needle deflection like above.