Question

A "sandwich" of cardboard and another material separates a magnet and an iron nail. Inserting which of the following materials into the sandwich will cause the iron nail to fall away?

Answer 1

I am not really sure, but wouldn't inserting materials that can be magnetic like aluminium and iron take up the effect of the magnetic field applied by the magnet? So wouldn't non-magnetic materials allow a force to be applied to the nail?

Answer 2

I think wood and glass....

Answer 3

But why not paper?

Answer 4

Paper will stick to the two

Answer 5

Wouldn't that only happen if the paper was charged?

Answer 6

oh ur right. I was misreading the question the whole time -_-

Answer 7

SO is that your answer?

Answer 8

Iron is ferromagnetic, which means that in the presence of an external magnetic field, the electrons in the iron will align to BOOST the external magnetic field. We can calculate the induced magnetic field if we know the permeability of the material. Iron has a very high permeability (~200), while these other materials have very low (or negative) permeability.

The magnet on top of the sandwich represents an external magnetic field.

I would wager that only iron allows the nail to be held by the magnetic field.

Answer 9

What about the Aluminium?

Answer 10

Aluminum is not magnetic. It does not create a magnetic field of it's own when exposed to an external magnetic field.

Aluminum is known as as non-magnetic material.

Answer 11

Thanks @eashmore