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What is magnetism?

  1. Oct 5, 2016 #1
    For a start, I must say that I'm just very interested in physics and maths but have no real education in these subjects.
    Does magnetism behave like other forces? Is the speed of the magnetism limited by lightspeed? Is it a wave or a particle, or both like light.
    Now for gravity, we have discovered 'gravity waves' but again is a particle too.
  2. jcsd
  3. Oct 5, 2016 #2
    The magnetic field is an effect induced by a moving charged particle or electric current, the flow of charged particles (protons or electrons). The magnetic field exerts a magnetic force on any other moving charge or current present in the field.

    So let's say you have a moving charge ##q_1## and another moving charge ##q_2##. As ##q_1## moves with velocity ##\vec v_2##, it creates a magnetic field ##\vec B_1## in its surrounding vicinity (where ##q_2## is also present) which in turn exerts a magnetic force ##\vec F_{1,2}## on ##q_2## (as ##q_2## is also moving). These can all be put into an equation, $$\vec F_{1,2} = q_2 * \vec v_2 \times \vec B_1$$

    This is the same thing as $$\vec F_{1,2} = q_2 * \vec v_2 * \vec B_1 * sinθ$$

    ##\vec v_2##, ##\vec B_1##, and ##\vec F_{1,2}## can all be represented as geometric entities in three dimensional space, or vectors; vectors are described by stating their magnitude and direction.

    2261-004-DA113F82.jpg (image taken from Encyclopaedia Britannica)

    θ is the angle between ##\vec v_2## and ##\vec B_1##. In the above picture, θ = 90° because ##\vec v_2## and ##\vec B_1## are perpendicular to each other (the angle between them is 90°).
    Last edited: Oct 5, 2016
  4. Oct 5, 2016 #3
    Magnetism and the electric force are very closely related. They always come together, and they are mathematically entwined, so we say they are both parts of the electromagnetic force.

    The electromagnetic field spreads out over all space. We have to be clear on what we mean by "speed" when we are not talking about a solid object. It makes the most sense to talk about the speed of propagation of changes in the field. If you move a magnet, then the field around the magnet takes some time to update. The speed at which the changes are propagated outward is the speed of light, precisely because the wave of propagation is light. Light is just an electromagnetic wave, and these waves carry changes in the electric and magnetic fields.

    Gravity is similar to electromagnetism but more complicated since more numbers are needed to describe the gravitational field at each point in space. We don't yet know if gravity can be described as particles, since a graviton has never been detected.
  5. Oct 5, 2016 #4
    Magnetism is a phenomenon, given to us by all the electrons spinning in the same direction, or the with the same angular momentum within ferrous metals. Magnetism and the electric field are friends like the yin and the yang. Together they form a field or a wave such as a radio wave. You cannot have one without the potential of having the other! Kinda like a handshake...It takes two.

    Magnetism is fleeting and not understood entirely. Without magnetism indeed, our perceived universe would be sorely bent and very different it has been decreed...
    Last edited: Oct 5, 2016
  6. Oct 5, 2016 #5

    Vanadium 50

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    Not so.
  7. Oct 5, 2016 #6
    So everything has a degree of magnetism, via the electromagnetic spectrum, which is everything. Magnetism is part of the electromagnetic spectrum, should have worked that out by the name! Thanks everyone for the answers.
  8. Oct 5, 2016 #7


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    Well, only in the sense that everything has a VALUE for its degree of magnetism. That degree will be zero, I believe, for something like a crystalline lattice (a diamond for example).
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