Maxwell's Equation: Magnetic B Field from Moving Charges

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In summary, a moving electric charge always produces a magnetic field according to the Laws of Biot and Savart, which can be expressed in terms of electric current or point charges. When the velocity of the charge is much smaller than the speed of light, the electric and magnetic fields can be approximated using the Biot-Savart law for a point charge, first derived by Oliver Heaviside in 1888.
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martin f
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Under what circumstances does a moving electric charge fail to produce a magnetic field?and what is the equation for finding the magnetic B field produced by multiple charges moving in a vacuum?
 
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martin f said:
Under what circumstances does a moving electric charge fail to produce a magnetic field?and what is the equation for finding the magnetic B field produced by multiple charges moving in a vacuum?
A moving electric charge always generates a magnetic field. The Laws of Biot and Savart describe how the magnetic field is generated by the electric charge. Although the expressions for this law often are written in terms of electric current, there are expressions appropriate for point charges.
Here is a link that may help.
http://en.wikipedia.org/wiki/Biot–Savart_law
“In the case of a point charged particle q moving at a constant velocity v, then Maxwell's equations give the following expression for the electric field and magnetic field:[
<connect to link to see the equations in reference>


When v2 ≪ c2, the electric field and magnetic field can be approximated as
<connect to link to see the equations in reference>

These equations are called the "Biot–Savart law for a point charge"[6] due to its closely analogous form to the "standard" Biot–Savart law given previously. These equations were first derived by Oliver Heaviside in 1888.
 

1. What is Maxwell's equation for the magnetic field from moving charges?

Maxwell's equation for the magnetic field from moving charges is a fundamental equation in electromagnetism that describes the relationship between the magnetic field (B) and the movement of electric charges. It is given by B = μ0I/(4πr), where μ0 is the permeability of free space, I is the current, and r is the distance from the moving charge.

2. How do moving charges create a magnetic field?

Moving charges create a magnetic field because they have an electric current associated with them, and according to Maxwell's equation, a magnetic field is produced whenever there is a current. This means that any time a charged particle moves, it creates a magnetic field around it.

3. What is the significance of Maxwell's equation for the magnetic field from moving charges?

Maxwell's equation for the magnetic field from moving charges is significant because it is one of the four Maxwell's equations that form the basis of classical electromagnetism. It helps us understand how magnetic fields are produced and how they interact with electric fields, which is essential for many modern technologies.

4. Can Maxwell's equation for the magnetic field from moving charges be applied to all types of moving charges?

Yes, Maxwell's equation for the magnetic field from moving charges can be applied to all types of moving charges, as long as the charges are in motion and produce a current. This includes both macroscopic and microscopic charges, such as electrons and protons. However, the equation may need to be modified for very high speeds or strong magnetic fields.

5. How does the magnetic field from moving charges differ from the magnetic field from a permanent magnet?

The magnetic field from moving charges is different from the magnetic field from a permanent magnet because it is produced by the movement of electric charges, while a permanent magnet has its own intrinsic magnetic field due to the alignment of its atomic dipoles. The strength and direction of the magnetic field from moving charges can also be changed by altering the current, whereas a permanent magnet has a fixed magnetic field.

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