Magnetic shielding works on the principles of the faraday cage
, except in reverse in the above example. If you have a strong conductor
surrounding your dipole
, any transient
s created by the dipole are equalized inside the conductor instead of your cathode ray tube
. Magnetic shielding is also a good thing to have on your monitor if you're worried about getting TEMPEST
ed by someone unsavory. When Bill Clinton
gave his closed-circuit
grand jury deposition
in the Lewinsky
case, the TV set he appeared on was shielded for just this reason.
Most of the time, however, designers put magnetic shielding on a piece of equipment because they're worried about outside magnetic currents effecting their own gadget. Computers are a good example of this, and entire labs can be magnetically shielded if they are doing any sort of research with radiofrequency applications.