Massachusetts Institute of Technology
Sign in

MIT Physics Demo -- Back "emf" in a Large Solenoid

A large solenoid is connected to DC power through a knife switch. When the switch is closed, the current builds up to approximately 30 amps. When the switch is opened, the solenoid attempts to keep the current flowing, creating a huge emf which ionizes the air in a huge spark.

Read more about inductors and emf.

Comments (1)

The phrase "solenoid attempts to keep the current flowing" is not very descriptive and somewhat incorrect. Once the current in the inductor reaches a steady 30 amps the magnetic field formed around the solenoid is stable. When the power source is removed the field collapses at very high rate of speed. This very fast moving magnetic field causes a reverse emf in the coil that creates the spark. -RH

Posted almost 9 years by Anonymous User

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

April 09, 2008 13:34
Creative Commons Attribution-NonCommercial (What is this?)
Additional Files

71465 times

More from MIT Department of Physics Technical Services Group

Fire Extinguisher on a Tricycle

Fire Extinguisher on a Tricycle

Added almost 9 years ago | 00:00:53 | 41844 views

MIT Physics Demo -- Telegraph Transmitter

MIT Physics Demo -- Telegraph Trans...

Added over 9 years ago | 00:00:36 | 55777 views

Speed of a Bullet

Speed of a Bullet

Added 9 years ago | 00:00:22 | 48954 views

MIT Physics Demo -- Microwave Interference

MIT Physics Demo -- Microwave Inter...

Added over 9 years ago | 00:02:11 | 31280 views

MIT Physics Demo -- Driven Mechanical Oscillator

MIT Physics Demo -- Driven Mechanic...

Added over 9 years ago | 00:01:07 | 41699 views

Cloud Chamber

Cloud Chamber

Added over 8 years ago | 00:02:36 | 95296 views