how does copper a copper cage keep out electromagnetic waves?
463517
the external electric field creates an electric field in the copper. however, copper is a conductor so charge flows within the copper so that the net electric field is 0.
212243
The Crystal radio, as it is offen referred to, uses a Germanium diode, instead of a Silicon diode.  A germanium diode has a lower forward bias voltage (0.3V, typ) so it's better for signal detection.\n\nThe tank circuit resonates at the tuned frequency, so it is able to build up a voltage just high enough to forward bias the diode.  This resonation could be compared to the act of swinging on a swing.  One small pump by itself does not create much movement, but a series of several small pumps in step (in tune) with the swinging action will get you going quite well.  So, the relatively weak radio signal continues to pump the LC tank circuit until it reaches equilibrium with the natural losses in the circuit, including the inductor resistances, wire resistances and the earpiece.\n\nThe name, tank circuit, was in respect to the capacitors used in early radio systems that were immerseed in metal tanks full of oil, which provided a higher dielectric breakdown voltage than air.
634155
You can do what they do for airliners to protect them for radio interference.  Since an EMP is just a very concentrated radio wave this should work.  Take some tin mesh and wrap it around the electronic device you wish to protect.  This will create a great barrier because it causes the radio wave to be absorbed by it, with no damage to the electronics inside it.
999979
The signal from the satellite is a microwave signal of a little more than a centimeter in wavelength. That means they will not pass through any metal with a hole smaller than that dimension, but instead are reflected. Microwaves are reflected from metal very much like light is reflected from metals. The satellite dish that appears to be plastic or fiberglass actually has metal embedded within it. Any type of metal, including copper, will work. The metal most commonly used is aluminum or steel.\n\nThe metal mesh is not used because of its conductive properties. Its conductivity is irrelevant. It is acting as a reflector and because of the parabolic shape of the dish is reflecting the signal in concentrated form into the receiver that sets over the front of the dish. \n\nI seriously doubt that any satellite dishes have silver in them, and using copper would be a waste of money, since copper is much more expensive than steel or aluminum. It is even possible to build a satellite dish out of chicken wire or screen wire. The wire is close enough together to reflect the microwaves. However, the shape is critical, and the plastic or fiberglass is designed to keep the critical shape. \n\nHere are some diagrams:\nhttp://www.mlesat.com/antennas.html\nThe microwave spectrum (in centimeters):\nhttp://meted.ucar.edu/npoess/microwave_topics/overview/print.htm#s1p2\nManufacture of dishes:\nhttp://www.madehow.com/Volume-1/Satellite-Dish.html
300790
Here's a link for annealing copper wire.  I don't know if that's what you want.
23795
How Stuff Works, my favorite site for things like this question.\n\nhttp://home.howstuffworks.com/metal-detector.htm
56086
Depending upon your application, copper probably does not make a good coil core.  If you wrap many turns of wire around a steel nail and pass a current through the wire (say from a battery) the nail will concentrate the magnetic field and you will have an electromagnet in which the tiny magnets within the steel are all aligned.  This will not happen with copper because you can not pick up copper with a magnet.  The coil will still produce a magnetic field but the copper core will not concentrate it.
226823
you can't block or absorb, but can always divert it. get a cage of good ferro-magnetic material, and magnetic field will not pass inside the cage. \n\nIt is similar to electric charge.
266957
The PHYSICAL PHENOMENON here is called ELECTROSTATIC SHIELDING!\n\nIt says that electrostatic field inside a hollow metal conductor is ZERO! \nThe field will be zero even if the conductor encloses a charge!\n\nHere the CAR can be considered as the conductor,\nSo! even if there is  a million volts of lightning outside! You are safe inside!\nThanks- Hope I helped\nPeace!
676026
Wild guess here... a dihydrate of copper chloride.\n\nSecond guess would be copper sulfate, possibly from the manufacturing process.
34105
The electromagnetic radiation from electrical devices COULD be used to induce a tiny current in a conductor, and used for some purpose. However, energy efficient devices experience very little leakage of radiation at these frequencies, or else they would violate FCC rules and interfere with a lot of other things. The biggest source of electromagnetic radiation from these devices is probably infrared radiation, or heat, which you could use to heat your home or for other purposes.
226234
I'm assuming here that you're building a protective casing around something.\n\nYou still may be able to use metal: If you want the magnetic transparency to be for the purposes of transmitting a signal, you could try making the casing itself your antenna. But, this may only work over short distances, as the shape of any casing is likely to be a poor antenna. You might try attaching an aerial (an antenna that sticks out) to a part of the casing that won't be subject to impact, if there is such a part. If the magnetic field is to provide a locomotive force to something inside the casing, but not the casing itself, then yeah, you probably can't use metal.\n\nIf you can't get ahold of kevlar, you might try wood (try a sturdy laminate, and don't be afraid to reenforce the structure with crossbeams or just thicker material) or other plastics (solid nylon comes to mind -- check around for a plastic shop that will be able to provide you with the material and machine it for you). Stone and concrete are very hard, but probably too hard: they lack resilency, and thus tend to chip and crack.
863889
Copper is used as a conductor and as a easily maliable (formable) metal.  It is also naturally anti-bacterial.
994725
An electromagnet is an iron core with wire wrapped around it so that the magnetic field that forms at a right angle to the direction of current becomes intensified in a specific location.  The reason for using insulated wire in an electromagnetic device is that it is not the current (electron frequency) moving through the wire that the engineer is interested in, but the automatic magnetic field that forms outside the wire.  This field is able to be formed, collapsed and reversed whenever one wishes to do so.\n\nA gravitational field (as our planet for example) is always one directional and the direction of energy flow is toward the core point of our planet.  Below the Moho line mass has its gravitational waves all focused toward the core point.  This means that all gravitational waves below that line pass through the very center of our planet and attract all mass directly on the opposite side, and at the same time also attracts all the heat energy of our planet to the core point.  If this were not true, then our planet would have (nearly) the same temperature throughout.
919740
In general the shielding of a cable (or electronic cct.) is metallic covering to protect against undesired signals from outside which may affect the performance of the device or the system.\nShielding mainly used in communication cct's , tuners , alarm system cct's and any application may affect or disturbed by the signals in the neighbor.\nthere are many types of shielding depending on the application:for cables we may find the mesh shield , aluminum sheath shielding, and other. For electronic cct shielding it is usually a metallic enclosure containing the cct.\none other thing, that some applications or devices during normal operation generating a high frequency signals with high power ,these devices must be shielded to prevent these signals from spreading outside.\nat last : ANY SHIELD FOR ANY APPLICATION MUST BE CONNECTED TO EARTH (MUST BE GROUNDED PROPERLY).
697337
Mostly they use magnetic fields.
1176223
There are few things that can actually stop a wireless signal, one of which is certain types of aluminum. Another thing, for example, is direct distance in feet. A room "right next to it" could actually be a greater physical distance than the room above it.