Moving Point Charge

Page claimed by James Moroz Jmoroz3 (talk) 11:47, 20 November 2015 (EST)

This page covers the method of calculating the magnetic field from a moving point charge, derived from the Biot-Savart Law for magnetic fields.

The Main Idea

A Mathematical Model

The magnetic field of a moving point charge can be found using a derivation of the Biot-Savart Law for magnetic fields.

With this equation for the magnetic field given some current carrying object, we can rewrited Idl in terms of velocity in order to relate the velocity of the moving particle to the magnetic field at an observation location a distance r from this particle.

With this substitution, the final formula comes out to be:

where q is the charge of the particle, v is the velocity of the moving particle, and r is the distance from the observation location to the moving particle.

Examples

Be sure to show all steps in your solution and include diagrams whenever possible

Simple

At a particular instant, a proton at the origin has velocity < 4e4, -5e4, 0> m/s. Calculate the magnetic field at location < 0.04, 0.05, 0 > m, due to the moving proton.

Middling

The electron in the figure below is traveling with a speed of [math]\displaystyle{ v = 5*10^6 }[/math]m/s. What is the magnitude of the magnetic field at location A if r = [math]\displaystyle{ 8*10^{-10} }[/math]m and [math]\displaystyle{ \theta=40 }[/math]degrees

Difficult

An electron is moving horizontally to the right with speed [math]\displaystyle{ 5*10^6 }[/math] m/s. What is the magnetic field due to this moving electron at the indicated locations in the figure? Each location is d = 7 cm from the electron, and the angle θ = 35°. Give both magnitude and direction of the magnetic field at each location.

Connectedness

A single moving point charge represents the most simple situation of charges moving in space to produce a magnetic field. In reality, this situation rarely occurs, however understanding how a single moving point charge interacts to produce a field will allow you to understand how sets of moving charges produce a field in space as well.

History

The history of the Biot Savart law and its discovery can be found at the Biot-Savart Law.

See also

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Further reading

Books, Articles or other print media on this topic

External links

Internet resources on this topic

References

http://maxwell.ucdavis.edu/~electro/magnetic_field/pointcharge.html This section contains the the references you used while writing this page