Ampere's Law

A much easier version of the Biot-Savart law that is useful for calculating the magnetic field within a closed path not a surface. This equation relates the magnetic field and the current to one another. Complete understanding of this topic makes other topics such as the nature of light easier to comprehend.

The Main Idea

A student is usually first taught how to find the magnetic field caused by the flow of individual charges and/ or currents. Ampere's law allows us to see a magnetic field and determine the currents that generate this field. Ampere’s law is a quantitative relationship between measurements of magnetic field a long a closed path and the amount and direction of the currents passing through that boundary. Ampere’s law is a quantitative relationship between measurements of magnetic field a long a closed path and the amount and direction of the currents passing through that boundary.

Here is a summary of the key steps in applying Ampere’s law:

1. Choose a (mathematical) closed path as a boundary.

2. Stretch an imaginary soap film over the boundary.

3. Walk around the boundary counterclockwise, integrating the field with the path.

4. Add up the positive and negative currents that pierce the soap film; this is ∑I inside path. Count as positive those currents that pierce the imaginary soap film coming out of the film (that is,in the direction of your right thumb with the fingers of your right hand curling around in the direction of your walk); currents that pierce the film going into the film are counted as negative.

5. Apply Ampere’s law, equating the two sums.

A Mathematical Model

[math]\displaystyle{ \oint_C \mathbf{B} \cdot \mathrm{d}\boldsymbol{\ell} = \mu_0 \iint_S \mathbf{J} \cdot \mathrm{d}\mathbf{S} = \mu_0I_\mathrm{enc} }[/math]

A Computational Model

How do we visualize or predict using this topic. Consider embedding some vpython code here Teach hands-on with GlowScript

Examples

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

Connectedness

1. How is this topic connected to something that you are interested in? While Ampere's Law doesn't directly connect to interesting stuff it does indirectly connect to some amazing things. For example magnetic fields can be used to expedites magnetic field calculations
2. How is it connected to your major?
3. Is there an interesting industrial application?

History

André-Marie Ampère, the founder of classical electromagnetism, was a French mathematician and physicist born into a merchant family. Due to his father’s strong beliefs, André was self-educated in his huge library. Fast forward about 30 years and André had become a well-established professor of mathematics, philosophy and astronomy at the University of Paris. In 1820, André had established what was later known as Ampere’s law. He was able to demonstrate that two parallel wires can be oriented, with different current flows, in a manner that let them either attract or repel one another. Your boy established a relationship between the length of a current carrying wire and the strength of their currents. In 1827-28, André was elected as a Foreign Member of the Royal Swedish Academy of Science and a foreign member of the Royal Swedish Academy of Science. In 1881, a while after his death in 1836, the ampere, a standard unit of electrical measurement, was named after him.

See also

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References

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Section 22.6 PATTERNS OF MAGNETIC FIELD: AMPERE'S LAW pg. 914- 920