Lets say I have a pipe and then another pipe inside a larger pipe.

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In summary, when using a coaxial cable with two pipes, one carrying an AC current and the other carrying the opposite AC current, there is no radiation outside of the pipes due to the cancellation of field amplitudes at large distances. This is due to the confinement of fields between the two pipes. However, there may still be a small amount of radiation within the space between the pipes, but it is unable to escape. This is known as a coaxial cable and is commonly used in technologies such as TV signals. If there was just one wire with an AC current, radiation would occur.
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cragar
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Lets say I have a pipe and then another pipe inside a larger pipe. On the inside pipe I have an AC current I(t) and on the outer pipe I have to opposite AC current -I(t). So that when I am outside both pipes and I make my Amperian loop, the current enclosed is always zero. Now my
question is will this radiate. Between the inner and outer pipe there should be a B field because I have enclosed current and it is changing with time so there should be an induced E field. So does the inner pipe radiate. Or what radiates if anything. Any input will be much appreciated. And the pipes are infinitely long.
 
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This doesn't radiate. It's called a coaxial cable and if you watch TV you're using it to get the signals.
 
  • #3


I don't understand why the inside one would not radiate. If I just had one wire with AC current would that radiate?
 
  • #4
cragar said:
I don't understand why the inside one would not radiate. If I just had one wire with AC current would that radiate?

If you had just one wire it would radiate.

With the coaxial cable, the fields are confined between the two pipes. So there is radiation of a sort, but it's being channeled to run down the space between the pipes and it can't get out.
 
  • #5


Another way to see why it doesn't radiate is that the two currents create field amplitudes at large distances that cancel each other out.
 

1. What is the purpose of having a pipe inside a larger pipe?

The purpose of having a pipe inside a larger pipe is to create a layer of insulation and protection for the inner pipe. This can help prevent damage to the inner pipe from external factors such as corrosion or impact, as well as provide a barrier for the contents flowing through the inner pipe.

2. How are the two pipes connected?

The two pipes are typically connected through the use of couplings or fittings. These are specialized hardware that allows for a secure and leak-proof connection between the two pipes. The type of coupling or fitting used will depend on the size and material of the pipes, as well as the purpose of the connection.

3. What materials are commonly used for the two pipes?

The materials used for the two pipes can vary depending on the specific application and environment. However, some commonly used materials include steel, PVC, copper, and HDPE. Each material has its own advantages and may be chosen based on factors such as cost, durability, and chemical resistance.

4. What are some benefits of using a double-pipe system?

A double-pipe system provides several benefits, including increased protection for the inner pipe, improved insulation to prevent heat loss or gain, and the ability to transport different types of materials through the two pipes simultaneously. It can also be more cost-effective than using a larger single pipe for the same purpose.

5. How do I determine the appropriate size for the two pipes?

The appropriate size for the two pipes will depend on factors such as the flow rate, pressure, and type of material being transported. A professional engineer or plumber can help determine the appropriate size based on these factors and any applicable building codes or standards.

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