Massachusetts Institute of Technology
Sign in

Adjustable Capacitor with Dielectric

First, an adjustable parallel-plate capacitor is held at a constant voltage. As the separation between the plates is widened, the electrometer shows charge (or current) flowing off of the plates, while the electroscope shows no change in voltage. Notice (by the deflection of the needle) that more charge flows off of the plates when they are closer together, and less when further apart. When the plates are brought back together, we see charge flowing back onto of the plates.

Next, we deposit a fixed amount of charge onto the left plate. Now, when the separation is widened, the electroscope shows a rising voltage, even as the amount of charge stays constant. When a block of plexiglass (a dielectric) is inserted between the plates, the voltage drops. However, when the plexi is removed, the voltage rises back up again, showing that the charge is still there.

This is one of the main reasons capacitors are built with dielectrics between their plates; more charge can be stored at a lower voltage.

Comments (1)

insert here

Posted almost 3 years by Anonymous 00:00:24

You need to log in, in order to post comments.

MIT Department of Physics Technical Services Group

MIT Department of Physics Technical Services Group

Category: Science | Updated over 6 years ago

Created
February 20, 2009 09:52
Category
Tags
License
Creative Commons Attribution-NonCommercial (What is this?)
Additional Files


Viewed
39238 times

More from MIT Department of Physics Technical Services Group

Balloons in Liquid Nitrogen

Balloons in Liquid Nitrogen

Added almost 8 years ago | 00:01:18 | 49799 views

MIT Physics Demo -- Microwave Interference

MIT Physics Demo -- Microwave Inter...

Added over 8 years ago | 00:02:11 | 30258 views

MIT Physics Demo -- Conductivity of Ionized Water

MIT Physics Demo -- Conductivity of...

Added over 8 years ago | 00:00:53 | 50449 views

Inducing Dipoles with a Van de Graaff Generator

Inducing Dipoles with a Van de Graa...

Added almost 8 years ago | 00:02:51 | 52349 views

Rotating Candles in a Dome

Rotating Candles in a Dome

Added over 6 years ago | 00:04:33 | 27982 views

Push Me, Pull You

Push Me, Pull You

Added 8 years ago | 00:01:42 | 37350 views