Andrew Gray, an electrical and computer engineering student at the University of Florida, demonstrates the computer-operated cart he made for his pet parrot. Complete with a four-direction joy stick, infrared sensors to prevent collisions, and bump sensors that automatically reverse the cart if it does hit something, this video is a fun and example of real-life application of STEM-related concepts.
On October 8th, 2012, magician David Blaine performed a seemingly life-threatening stunt subjecting himself to a whopping one million volts of electricity while wearing a 20-pound chain metal suit.
The public was shocked by the performance, a demonstration that seems to defy the basic laws of science. However, an understanding of the laws of electricity will show that Blaine was not working against these basic principles, but was using them in order to perform his trick successfully!
In the video of Blaine’s performance shown above, the magician is wearing a Faraday Cage – a type of suit made of a conductive material invented in 1836 by English scientist, Michael Faraday. The suit functions as a shield that blocks external static and non-static electric fields which causes the electric charges within the Cage’s conductive material to redistribute themselves and thus cancel the field’s effects in the cage interior. This same phenomenon explains why one is safe from lightning storms and other external electric fields while driving a car (not the rubber tires, despite what Grandma may have told you!)
So while Blaine’s performance looks pretty dangerous, his Faraday Cage (which, theoretically, has no voltage limit) prevents the electric current from reaching his body, making it not quite the superhuman feat it appears. Nevertheless, showing this video to your physics classes will have even the bravest students on the edge of their seats – until you explain the principles behind it!
Other common uses for a Faraday cage include:
- Your microwave oven & its door preventing the Radio Frequencies/Energy within the oven from leaking out.
- Elevators simulate a Faraday cage effect, leading to a loss of signal and “dead zones” for users of cellular phones & radios which require electromagnetic external signals.
- The shielding inside of coaxial television cable wire & USB cables protect the internal conductors from external electrical noise and prevents the RF signals from leaking out.
- Plastic bags impregnated with metal are included with highway electronic toll collection devices which are to allow motorists to place them in the bag so that a toll charge is not registered or a device will not register a charge while being shipped to a customer’s home after ordering in a delivery truck.
- Even MRI machine scan rooms are designed as Faraday cages to prevent external radio frequency signals from being added to data collected from the patient, which would affect the resulting image.
- Shopping bags lined with aluminum foil have even been found by police in arresting shoplifters who steal RF-tagged items; the bags acting as Faraday cages.