Skip Ribbon Commands
Skip to main content
SharePoint

5K10.80 - Faraday's Disc

The Web Part cannot find an InfoPath form in the specified location. Either the location does not have an InfoPath form associated with it or it is on a different site collection. Modify the Web Part Properties and select a list or library on the current site.

5K10.80 - Faraday's Disc

Preview
SelectSelected
Title5K10.80 - Faraday's Disc
Objective

​To demonstrate generation of DC voltage with the rotational motion of an electrically conductive disc in a plane perpendicular to a uniform static magnetic field.

StatusAvailable
Assembly Instructions

Attach a meter with a mV setting to the Faraday disc.  Using a 3M pad, clean the surface of the rotating disc to ensure there is a good connection between it and the brush commutator​.

Setup Time5
Operation Time5
Preview Time5
Operation Instructions

With the multimeter attached, spin the conductive disc in the direction indicated.  You should see a few milivolts generated by this apparatus.  Then switch the multimeter to the amp setting and observe the larger value of the current produced by this apparatus.​

NOTE:  This Faraday's Disc is NOT designed to be a motor and a generator due to the type of "brush" commutator that was used.

ExportableNo
Demo on DimeNo
PIRA 200No
Export Instructions (if different)
HazardsNone
Analysis/Information

​ Disk-type generator:  Also known as a unipolar generator, acyclic generator, or disk dynamo

One of the electrical contacts is near the axis and the other near the periphery. It has been used for generating very high currents at low voltages in applications such as welding, electrolysis, and railgun research.
 
In contrast to other types of generators, the output voltage never changes polarity. The charge separation results from the Lorentz force on the free charges in the disk. The motion is azimuthal and the field is axial, so the electromotive force is radial. The "brush" contact is an inefficient way to contact the disk due to the number of large losses that exist at the low voltages that are present.  Historically, mercury was used to provide constant contact, but due to the toxicity of mercury we do not use it.
 
When the magnetic field is provided by a perminant magnet, the generator works regardless of whether the magnet is fixed to the stator or rotates with the disc. Before the discovery of the electron and the Lorentz force law, the phenomenon was inexplicable and was known as the Faraday paradox.
Category5 Electricity and Magnetism
Subcategory5K - Electromagnetic Induction
Keywordsgenerator, faraday, disk,
Construction Information
 
Equipment TitleUse SHIFT+ENTER to open the menu (new window).
  
QuantityUse SHIFT+ENTER to open the menu (new window).
  
Faraday's disc generator
1
banana cable
2
multimeter - voltage DC
1
camera - b&w
1