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 4 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 7 years ago

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


Viewed
41001 times

More from MIT Department of Physics Technical Services Group

Hinged Stick and a Falling Ball

Hinged Stick and a Falling Ball

Added over 7 years ago | 00:01:23 | 24355 views

Potential Energy to Kinetic Energy

Potential Energy to Kinetic Energy

Added 9 years ago | 00:01:11 | 35891 views

Faraday's Cage

Faraday's Cage

Added almost 9 years ago | 00:01:23 | 71792 views

MIT Physics Demo -- Microwave Polarization

MIT Physics Demo -- Microwave Polar...

Added almost 10 years ago | 00:01:14 | 38925 views

Strobe of a Falling Ball

Strobe of a Falling Ball

Added over 9 years ago | 00:00:41 | 51043 views

MIT Physics Demo -- Magnetic Deflection of a TV Image

MIT Physics Demo -- Magnetic Deflec...

Added over 9 years ago | 00:01:35 | 65083 views