Relationship electricity and magnetism

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Discussion Overview

The discussion centers on the relationship between electricity and magnetism, exploring concepts such as electric fields, magnetic fields, and electromagnetic induction. Participants share their understanding and seek clarification on how these phenomena interact, particularly in the context of moving magnets and coils of wire.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant describes their understanding of electric charges and fields, noting how a negatively charged object can induce a charge in another object.
  • Another participant questions whether a moving magnet induces magnetism in a coil of wire, seeking clarification on the nature of the induced current.
  • It is stated that a stationary charged object generates an electric field, while a moving charged object generates a magnetic field.
  • Participants discuss that the magnetic field of a permanent magnet is generated by electrons moving in loops around atoms, and that an electromagnet's field is generated by electrons moving in larger loops within a solenoid.
  • Clarifications are made that a moving magnet induces an electric field rather than magnetism in the coil of wire.
  • One participant expresses confusion about how an electric field is created by a moving magnet and whether the movement of the magnet alone is sufficient to generate an electric field.
  • It is noted that the movement of a magnet does indeed create an electric field, and that the induced electric field causes electrons to move along the wire.
  • Participants discuss the nature of induction and the lack of a deeper "why" behind the phenomenon, attributing it to the mathematical structure of space-time.
  • One participant expresses a desire to continue learning about electricity and magnetism and seeks recommendations for study materials.

Areas of Agreement / Disagreement

Participants generally agree on the basic principles of electromagnetic induction, but there are nuances in understanding the relationship between electric and magnetic fields that remain contested. The discussion does not reach a consensus on all points, particularly regarding the nature of electric fields and their generation.

Contextual Notes

Some participants express uncertainty about the definitions and interactions of electric and magnetic fields, indicating a need for further clarification on the underlying principles of electromagnetism.

Who May Find This Useful

This discussion may be useful for individuals seeking to understand the foundational concepts of electricity and magnetism, particularly those new to the subject or returning to it after a long absence from formal study.

t1mm3h
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Hello, I have started reading a beginners book (from the "stop faking it" series) on electricity and magnetism. Its supplied with funny little experiments to help me understand the topic. But I have trouble understanding the intimate relationship between electricity and magnetism. I believe I understand the model of atoms, protons and electrons and how electrons behave.

I'll try to show part of the picture I have gained now: a negatively charged object (let's say a rubbed balloon) can induce a charge in another object because the electrons repel the electrons in another object and attract the protons. As a result, the distance between the electrons of the balloon and the protons of the other object is smaller and they attract each other. So I get the topics of charges, electrons' tendency to move and make objects neutral, and electric fields as a result of charging an object.

Now when it comes to magnetism I see how bar magnets interact in the sense that the magnetic force tends to "line them up". Also I took the point that electrons themselves are like tiny magnets. When a coil is connected to a battery and wrapped around, for example a screw, it creates a bigger magnetic field and leaves the screw magnetized for a while.

Now what I do not understand is when you have a coil of wire and you move a magnet in and out, a current starts to flow. Is the magnet inducing magnetism in the coil of wire? So the electrons "want to" line up with the magnetic field of the magnet, and that's why they start flowing and create current?

I also do not understand this sentence in the book I am reading: "A changing magnetic field generates an electric field". I see a magnetic field a result of a charged object (like the balloon has a magnetic field around it).

Some help on clearing this up would be great!
 
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hi t1mm3h! :smile:
t1mm3h said:
Now what I do not understand is when you have a coil of wire and you move a magnet in and out, a current starts to flow. Is the magnet inducing magnetism in the coil of wire? So the electrons "want to" line up with the magnetic field of the magnet, and that's why they start flowing and create current?

I also do not understand this sentence in the book I am reading: "A changing magnetic field generates an electric field". I see a magnetic field a result of a charged object (like the balloon has a magnetic field around it).

Some help on clearing this up would be great!
 
hi t1mm3h! welcome to pf! :smile:
t1mm3h said:
I also do not understand this sentence in the book I am reading: "A changing magnetic field generates an electric field". I see a magnetic field a result of a charged object (like the balloon has a magnetic field around it).

no: a stationary charged object generates an electric field, a moving charged object generates a magnetic field

the magnetic field of a permanent magnet is generated by the electrons moving in tiny loops around their atoms

the magnetic field of an electromagnet is generated by the electrons in the solenoid moving in large loops

so long as the magnet is not moving, or the current in the electromagnet is not changing, there is no electric field (ie only a magnetic field)

when it changes, an additional electric field is created
Now what I do not understand is when you have a coil of wire and you move a magnet in and out, a current starts to flow. Is the magnet inducing magnetism in the coil of wire?

no, the magnet is inducing an electric field

that electric field makes the electrons move in the usual electric way :wink:
 
Thanks for your reply tiny-tim.

1) So if the magnet induces an electric field, is the solenoid (the stationary object) becoming charged temporarily (as the magnet moves in)?

2) To go to a lower level: as far as I can see, a magnet can cause electrons to "line up" with the magnetic field. Is this why an electric field is induced?
 
hi t1mm3h! :smile:
t1mm3h said:
1) So if the magnet induces an electric field, is the solenoid (the stationary object) becoming charged temporarily (as the magnet moves in)?

no, the wire in the solenoid remains electrically neutral

all that happens is that the positive charges remain stationary, while the negative charges (the electrons) start moving along the wire

no charge is created
2) To go to a lower level: as far as I can see, a magnet can cause electrons to "line up" with the magnetic field. Is this why an electric field is induced?

no, the electrons "line up" whether the magnet is moving or not

(and it is only their spins that line up)

anyway, the electric field is created (by a moving magnet) whether there are any electrons there or not
 
tiny-tim said:
while the negative charges (the electrons) start moving along the wire

Okay so what causes the electrons to move? Is it the induced electric field? I guess I still don't fully understand how an electric field (yes I read the pf definition) comes into existence due to a magnet. Does the movement of the magnet solely create a electric field? If I hold a bar magnet in my hand and move it up and down, do I create an electric field...?
 
t1mm3h said:
Okay so what causes the electrons to move? Is it the induced electric field?

yes, the electrons move only because there is an electric field
I guess I still don't fully understand how an electric field (yes I read the pf definition) comes into existence due to a magnet. Does the movement of the magnet solely create a electric field? If I hold a bar magnet in my hand and move it up and down, do I create an electric field...?

yes you do

basically induction happens because it happens, there isn't really a "why" (other than the mathematical structure of space-time)
 
I know physics isn't here to answer why questions, it just explains what we observe for a great deal.

So we can conclude that a changing magnetic field generates an electric field because we see charges in the wire moving. And we know that charges move because of electric fields. Right?

Thanks for the great help so far! I think I can continue reading my book now and start learning more. Any recommendations on material for understanding electricity/magnetism?
 
t1mm3h said:
So we can conclude that a changing magnetic field generates an electric field because we see charges in the wire moving. And we know that charges move because of electric fields. Right?

yes … that's science! :smile:
Thanks for the great help so far! I think I can continue reading my book now and start learning more. Any recommendations on material for understanding electricity/magnetism?

what stage of education are you at?
 
  • #10
Great I get it. Thanks again tiny tim.

Well I already studied at university level but I studied social sciences. I dropped physics and chemistry about 10 years ago in the beginning of secondary school. Now I want to (re)learn at least the basics of science (physics, chemistry and biology) by doing self-study.
 
Last edited:
  • #11
t1mm3h said:
Well I already studied at university level but I studied social sciences. I dropped physics and chemistry about 10 years ago in the beginning of secondary school. Now I want to (re)learn at least the basics of science (physics, chemistry and biology) by doing self-study.
t1mm3h said:
Any recommendations on material for understanding electricity/magnetism?

(i wouldn't bother about magnetism)

you could try scientific american (monthly) …

it has quite long but well-explained articles, and you could use them as a basis for further study

(and if you want to subscribe, pf members can get https://www.physicsforums.com/partners.php)
 

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