Grappling with a Magnetism question

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In summary, when using Ampere's law to find the B field between the outer and inner cables of a coaxial cable, the B field will only be dependent upon the current running through the inner wire. This is because the contributions from different parts of the conductor cancel each other out, resulting in no field inside a hollow cylindrical conductor. The B-field is also dependent on the radial distance of the particular point from the inner wire. This means that the B field is not dependent on the current in the outer concentric wire.
  • #1
sharpstones
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When analyzing a coaxial cable and trying to find the B field in the space betwen the outer and inner cables, using ampere's law the B field will be depedent only upon the current running through the inner wire.

Why is this? I know that yes Ampere's law says that only the current contained within the amperean loop can cause a B field, but i want a better explanation then that. Let's suppose there was just a plain hollow cylindrical conductor with current running through it. Would there be a B field running through it?
 
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  • #2
The better explanation is in writing the field due to several elemental sections of the conductor, using Biot-Savart's Law and integrating over the entire conductor. Unfortunately, it's a mathematical explanation, not a physical demonstration.

The only physical thing that can be said (this amy seem obvious) is that the contributions from different parts of the conductor cancel each other out in the case of say, the hollow conductor. So, the answer to that part is "No, there will be no field inside a hollow cylindrical conductor".

To answer the first part, the B-field is not dependent on only the current. It is also dependent, in this case, on the radial distance of the particular point.
 
  • #3
regarding the first part. I wasn't very specific... what I ment was that i was suprised to find that it was dependent upon the curreny on the inner wire, but non dependent at all on the outer concentric wire.
 

FAQ: Grappling with a Magnetism question

What is magnetism?

Magnetism is a physical property of certain materials that causes them to attract or repel other materials. It is caused by the movement of electrons within the material.

How does magnetism work?

Magnetism works through the alignment of magnetic domains within a material. These domains are groups of atoms with their magnetic fields pointing in the same direction, creating a strong magnetic force.

What are the types of magnetism?

The three main types of magnetism are ferromagnetism, paramagnetism, and diamagnetism. Ferromagnetism is the strongest and is found in materials like iron, nickel, and cobalt. Paramagnetism is weaker and is found in materials like aluminum and platinum. Diamagnetism is the weakest and is found in materials like copper and gold.

How can magnetism be measured?

Magnetism is measured using a device called a magnetometer. This device can measure the strength and direction of a magnetic field.

How is magnetism used in everyday life?

Magnetism is used in many everyday objects, such as refrigerator magnets, speakers, and electric motors. It is also used in medical imaging technology, like MRI machines, and in data storage devices, like hard drives.

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