Who defined the positive direction of the magnetic field?

Thread starter Jairo Amaral
Start date Feb 11, 2019
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Convention Direction Field Historical Magnetic Magnetic field Positive

In summary: It's neither work nor formal study, so it isn't urgent. But I plan to write about science for lay people in the future, so it'd be nice to know.

Jun 13, 2022

kuruman

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vanhees71 said:

It's much clearer, not to mention the Earth and compass needles first but just use magneto statics a la Ampere and define everything in terms of vectors (magnetic field, B→, and, if you want to deal with permanent magnets, magnetization).

I think the confusion arises because of poor understanding of the dipolar field.

People know that two bar magnets line up [S-N] [S - N]. They would then assume that if we model the Earth as a bar magnet, we will also have [Earth] [Compass needle] ⇒ [S - N] [S - N] failing to realize that this happens only at the magnetic poles. It is natural to assume that the Earth's magnetic field, just like its gravitational field, has a non-zero divergence. I too had that misconception until I learned some physics.

<h2>1. What is the positive direction of the magnetic field?</h2><p>The positive direction of the magnetic field is the direction in which a north magnetic pole would move when placed in the field. It is conventionally represented by an arrow pointing towards the north pole of a magnet.</p><h2>2. Who defined the positive direction of the magnetic field?</h2><p>The positive direction of the magnetic field was first defined by French physicist and mathematician André-Marie Ampère in the early 19th century. He established the convention of using the right-hand rule to determine the direction of the magnetic field around a current-carrying wire.</p><h2>3. Why is the positive direction of the magnetic field important?</h2><p>The positive direction of the magnetic field is important because it allows us to establish a consistent and universal convention for describing the direction of magnetic forces and fields. This convention is used in various fields of science and engineering, such as electromagnetism and magnetohydrodynamics.</p><h2>4. How is the positive direction of the magnetic field related to the Earth's magnetic field?</h2><p>The Earth's magnetic field is aligned with the positive direction of the magnetic field, with the north magnetic pole located near the geographic South Pole and the south magnetic pole near the geographic North Pole. This means that the Earth's magnetic field is directed from south to north, which is opposite to the direction of the magnetic field of a bar magnet.</p><h2>5. Can the positive direction of the magnetic field be reversed?</h2><p>Yes, the positive direction of the magnetic field can be reversed by reversing the direction of the current flow or by flipping the orientation of a magnet. This is known as magnetic reversal and has been observed in the Earth's history, where the north and south magnetic poles have switched positions multiple times.</p>

1. What is the positive direction of the magnetic field?

The positive direction of the magnetic field is the direction in which a north magnetic pole would move when placed in the field. It is conventionally represented by an arrow pointing towards the north pole of a magnet.

2. Who defined the positive direction of the magnetic field?

The positive direction of the magnetic field was first defined by French physicist and mathematician André-Marie Ampère in the early 19th century. He established the convention of using the right-hand rule to determine the direction of the magnetic field around a current-carrying wire.

3. Why is the positive direction of the magnetic field important?

The positive direction of the magnetic field is important because it allows us to establish a consistent and universal convention for describing the direction of magnetic forces and fields. This convention is used in various fields of science and engineering, such as electromagnetism and magnetohydrodynamics.

4. How is the positive direction of the magnetic field related to the Earth's magnetic field?

The Earth's magnetic field is aligned with the positive direction of the magnetic field, with the north magnetic pole located near the geographic South Pole and the south magnetic pole near the geographic North Pole. This means that the Earth's magnetic field is directed from south to north, which is opposite to the direction of the magnetic field of a bar magnet.

5. Can the positive direction of the magnetic field be reversed?

Yes, the positive direction of the magnetic field can be reversed by reversing the direction of the current flow or by flipping the orientation of a magnet. This is known as magnetic reversal and has been observed in the Earth's history, where the north and south magnetic poles have switched positions multiple times.