Last Week's Question
Of the following choices, the best material to use to shield a 60 Hz magnetic field is,
- either "b" or "c"
The correct answer is "b". None of these materials has a high enough conductivity to block a magnetic field using eddy currents at 60 Hz. The best remaining option is to redirect the field using a material with a high relative permeability. The relative permeability of copper and lead is close to 1 (about the same as plastic or air). The only material in this list that potentially has a high relative permeability is steel.