From Oersted experiment we know " When an electric current is passed through a conducting wire, a magnetic field is produced around it." An electric current is a flow of electric charge or electron. My question is "How does a flow of electron or electric charge create magnetic field?"
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asked Feb 28, 2018 at 8:59
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$\begingroup$ @MohammadMizanurRahaman...You should consider the case of special relativity here... $\endgroup$– Nehal SameeCommented Feb 28, 2018 at 9:16
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$\begingroup$ I am just a 11th grade student.My concepts about SR is very dim. Isn't it possible to explain this question without SR? $\endgroup$– Mohammad Mizanur RahamanCommented Feb 28, 2018 at 9:26
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3$\begingroup$ Not really. Without SR, magnetism is pretty much best explained as a fundamental phenomenon. You can't really explain why it happens any more than you can explain why a stationary charge has an associated electric field. $\endgroup$– Chris ♦Commented Feb 28, 2018 at 9:44
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2 Answers
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I would suggest watching this by Veritasium.
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.
answered Feb 28, 2018 at 10:22
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$\begingroup$ The metaphor of understanding the topic in video is awesome.Now it is almost clear to me $\endgroup$ Commented Mar 3, 2018 at 8:32
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The short answer is because a moving charge induces a magnetic field.
The longer answer has to include what we observe and what we we have to deduce. Oersted has observed that a moving in circles electron (the current in the coil) led to a magnetic field. How that happens in detail:
Moving in circles a body experience an acceleration. Why it is important to mention this fact? Because under this acceleration the electrons spins get aligned. And the intrinsic magnetic dipole moment of the electron gets aligned together with its spin! So the magnetic field of the coil is the sum of the magnetic dipole moments of the involved electrons.
answered Feb 28, 2018 at 9:27
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$\begingroup$ I thought about spin of electron but not in this way. But what do you mean by "the intrinsic magnetic dipole moment of the electron gets aligned together with its spin"? I can't realise this line poperly $\endgroup$ Commented Feb 28, 2018 at 9:39
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$\begingroup$ @MohammadMizanurRahaman ... The alignment of dipole moments produces polarity in the conductor... $\endgroup$ Commented Feb 28, 2018 at 9:59
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$\begingroup$ Do you want to say this polarity originate the field? $\endgroup$ Commented Feb 28, 2018 at 10:01
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$\begingroup$ To understand it at a more fundamental level , you need to go through the Maxwell's equations as to why changing electric field induces magnetic field. $\endgroup$ Commented Feb 28, 2018 at 10:02
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$\begingroup$ @NehalSamee The Maxwell equations describe the observations, but they don't explain the reason for the magnetic field. I also wonder how HolgerFiedler's answer aligns with the possible duplicate answer, explaining the magnetic field as a consequence of special relativity. $\endgroup$ Commented Feb 28, 2018 at 10:23