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Q & A: Magnetism, Electricity, and Stuff that doesn’t Conduct

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Most recent answer: 10/22/2007
Q:
Why magnetism can pass though wood, plastic, ect. but electricity can’t.
- Jason (age 11)
Pompano Beach
A:
Jason -

I think what's getting you confused here lies in the basic differences in how we use magnetism and electricity.
Most objects are almost non-magnetic. Magnetic objects are surrounded by magnetic fields. When one magnet id in the field of another, there's a force on it. These fields are not affected by non-magnetic objects, so the forces between magnetic objects are not changed much by most things that might happen to be between them.

Electrically charged objects also are surrounded by fields- electrical fields. These fields also can go right through many objects. If you make some big electric fields on one side of a sheet of some typical non-conducting plastic, those fields can be measured on the other side of the plastic, just like magnetic fields could.

When you write that electricity can't pass through plastic, you're probably thinking of electric currents. Those consist not of electric fields but of actual moving electrically charged particles. In many materials the charged particles are pretty much stuck to atoms and can't flow. That includes many plastics. Other materials, like metals and some plastics, have electrons that are free to move so they do support electrical currents. These same materials interfere with electrical fields, because the charges move to partly cancel the fields from other charges.

-Tamara (and mike)

(published on 10/22/2007)

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