Natural Science Forum / Physics / Electromagnetism / October 2005

A few simple questions. What materials are good for protection from
various frequencies of electromagnetic radiation? From school physics
I remember that lead is supposed to be best? Do other metals such as
iron or aluminium offer any barrier?

I wish to build an experimental device that is designed to show the upward
displacement of a wire as it is rotated in a magnetic field produced by two
magnets.
as I understand it, the force that is going to produce this displacement is

i dont know if i am on the right news group...
i have a problem in my physic group 4 project with is about
magnetic force produced by 2 magnets and where i am block is
i got 2 magnet from old speakers and i dont know how to get there

Hi one and all, I have a bit of a problem and need some urgent help.
hopefully some kind soul out there can drag me out, or help me somehow.
right, I am using F=BilSin theta to work out the vertical force produced by
a magnetic field on a wire rotating between two magnets.

Well, it is beyond my capability of analysis.
The problem is:
We have a closed current loop with current I, fixed somewhere in space. Then
the magnetic field at any point is:

I have a little question, please help me out:
Some books claim or suggest that non-localised classical wave models have
been disproved, and until now I swallowed that. However, now I have some
doubts about that (triggered by a paper of Poincare). Now, if such claims

This should be of interest to this group:
The latest edition of the free Motion Mountain physics text can be
downloaded at
          http://www.motionmountain.net/welcome.html

We assume to find in every point of space a flow in all directions of
radiant energy from all astrophysical objects, meaning that space
everywhere has a specific energy U erg and an energy density u = U/V
erg/cm^3, which of course is a local variable depending on the position

I have this Qs since few months and last night watching the Horizon on BBC
about Hawking I am compelled to ask it.
According to the Horizon, Hawking asked the same Qs 30 years ago.
What if the universe together with its mathematical structure and physical