Like every object applies gravitational force to every other object. The reason can be in the General Theory of Relativity. In the same way why magnetic field applies force on moving charge (and why only on charge)?
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3$\begingroup$ Possible duplicate of How do moving charges produce magnetic fields? $\endgroup$– Nehal SameeCommented Mar 1, 2018 at 16:43
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$\begingroup$ This one is also highly relevant if not a duplicate: physics.stackexchange.com/q/228373/26076 $\endgroup$– Selene RoutleyCommented Mar 4, 2018 at 5:37
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2 Answers
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Special Relativity merges the domain of electricity and magnetism.
I would suggest watching this by Veritasium and Henry.
Suppose you are the charge and moving along a current carrying wire at a distance d from it.
Now the electrons in the wire relative to you are going backwards and since einstein proposed his laws, the electrons get a little squished relative to you.
So you will see that the electrons are crowded together and the wire is now not neutral relative to you, you will observe a electrostatic force. In the ground frame we call it magnetic force.
The electrostatic force is experienced by a charge only hence following the above logic magnetism will also act on a charge.
answered Mar 1, 2018 at 11:46
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$\begingroup$ Wow!! This is exciting !! Love Einstein...thanks for the answer. $\endgroup$ Commented Mar 1, 2018 at 14:43
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Why? Experimentally it does. That's all we can say in physics.
However, the fact that it does ties in elegantly with special relativity. We can give the following theoretical motivation for expecting such a relationship:
Given the following:
- If we postulate a linear, homogeneous relationship between a point charge's velocity and the electromagnetic force on a charged body;
- In special relativity, a massive point particle's four velocity vector must always have a constant Minkowski norm of $c^2$
Then it follows from these two postulates alone that the electromagnetic force must precisely decompose into two components: (1) a component that is proportional to the charge alone and independent of velocity together with (2) a component that is proportional to the charge and at right angles to the velocity. I discuss these inferences more in my answers here and here.
Of course, Nature could have choosen more complicated assumptions than our postulates, so the above is not a proof, but experimentally we observe that She doesn't.
answered Mar 4, 2018 at 5:36