Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [electromagnetism]

Electromagnetism is a branch of Physics involving the study of the electromagnetic force, a physical interaction that occurs between electrically charged particles. This force plays a major role in determining the internal properties of most objects encountered in daily life. Originally, electricity ...

7
votes
4answers
180 views

How did early scientists know if a current was changing direction? (AC vs. DC)

How did Faraday, Ampere and Hippolyte Pixii know that electricity 'traveled' at all? Let alone in a certain direction? And that it was reversing direction with certain early generators?
2
votes
1answer
44 views

Why is the amount of charge needed to generate 1 unit of electric flux, called permittivity?

This keeps confusing me. I keep imagining "permittivity" as being "The ability for a substance to permit electricity", when it is the opposite. High permittivity means it is hard (requires a lot of ...
0
votes
0answers
46 views

How did people in pre-Ampere period deduce this?

How did people before Ampere (eg-Coulomb) who used magnetic-pole model, know that only two surfaces (north and south poles) of a bar magnet exerts and experiences force while the rest of the surfaces ...
3
votes
1answer
94 views

Was the telegraph system of 1859 powered by AC or DC and how extensive was it?

I was actually curious how the Solar Coronal event of 1859 known as the Carrington Event affected the telegraph system. Wiki does not seem to have much detail of this but there is mention of it in a ...
5
votes
2answers
190 views

Historically how it was discovered that we need fields to describe matter?

This question is from one historical perspective. The question is: how physicists historically found out that one needs quantum fields to describe matter? Being more detailed. Let us consider the ...
4
votes
0answers
99 views

Several questions about Gauss's contributions to electromagnetism

First of all, i appologize if i'm asking too many questions about Gauss (and some will also say "not very interesting questions"); i know i might appear ridiculus - but i really think it's an ...
1
vote
0answers
134 views

How did Gauss's electrodynamics law preempt the later developement of retarded potentials theory in physics?

My question refers to a fragment on electrodynamics written by Gauss at around 1835. In this short note (see Gauss's werke, volume V, p. 616-617) Gauss wrote down a fundamental equation which ...
3
votes
3answers
76 views

Is there an anthology of classic papers on electricity?

I'm trying to find a book similiar to Stephen Brush "Kinetic Theory of Gases: An Anthology of Classic Papers With Historical Commentary". The electricity version, let's say! I like to see how subjects ...
1
vote
0answers
53 views

Who first noticed that the radiation pressure formula $p=U/c$ agreed with $E=pc$ from special relativity?

Does anyone know behind stories? As it seems that $p=U/c$ was known before the advent of special theory of relativity, (Halliday, Resnick, Walker says that Maxwell derived this.) when $E=pc$ was first ...
0
votes
0answers
33 views

Who first stated that electromagnetic radiation is the difference between advanced and retarded fields?

Dirac makes the claim in his 1938 paper, Classical theory of radiating electrons, that for an electron accelerated by an electromagnetic field: $$ F^{\mu\nu}_{act} = F^{\mu\nu}_{ret} + F^{\mu\nu}_{in}...
0
votes
1answer
71 views

Introduction of magnetic vector potential [duplicate]

Who first introduced the concept of magnetic vector potential and why? Was it introduced only for ease of mathematical calculation or it was done keeping in mind its physical significance like ...
12
votes
3answers
286 views

How did Milikan know that oil drops would acquire only few electron charges?

In the book of Experiment in Modern Physics, by Melissinos, at page 2, it is given that: 2. The Millikan Oil Drop Experiment In 1909, R. Millikan reported a reliable method for measuring ionic ...
0
votes
1answer
33 views

Capacitance or capacity?

In physics, the capacitance of a conductor is (roughly) the net charge accumulated when it is grounded relative to a unit voltage at infinity. The same quantity comes up in mathematics, but we call ...
5
votes
1answer
169 views

Who originally derived the general force law equation of force between current elements?

Wikipedia credits this to Maxwell. This derivation can be found in Maxwell's Treatise on Electricity and Magnetism vol. 2, part 4, ch. 2 (§§502-527). I went through the derivation and found two self ...
3
votes
0answers
79 views

Who was the first to use the term field in physics?

Faraday, after drawing his lines of force in 19th century, is normally credited as the first to use the term field in physics. But... ... was not the term field used in the context of gravitational ...
2
votes
1answer
212 views

Is it thought that Maxwell used Green's Theorem to derive his equations?

I noticed there are two varieties of Maxwell's equations and although I am not sure which form Maxwell originally worked with and perhaps the differential form came much latter, I was wondering if he ...
3
votes
2answers
164 views

When Was Kaluza-Klein Theory Appreciated?

As far as I understand the Kaluza-Klein theory, despite its unprecedentedly profound and beautiful character, had a modest following in its early days. I guess two of the many reasons might be the ...
4
votes
1answer
72 views

What/When was the first radio nav system capable of triangulating your position?

What was the first radio navigation system capable of triangulating your position, and when was it built? How accurate was it and what was its range? This does not have to be GPS or a satellite ...
3
votes
0answers
49 views

During the development of QFT was this theory actually used to build any invention like the MRI?

I have always wondered if the equations of quantum field theory were actually ever used in the production of some invention or device other than needed to make predictions about the Standard Model of ...
0
votes
1answer
43 views

History of Magnetism before the Hubbard model

I'm interested in models used before the Hubbard model (free electron model, band model, etc, both itinerant and localized models). What were their strengths and weaknesses? Which model is currently ...
3
votes
3answers
258 views

“Tension” between Electromagnetism and Newton's laws

When talking about the inconsistencies in physics that led up to Einstein's discovery of relativity today's professors always say that Maxwell's discovery of the constant speed of light $c$ created a ...
0
votes
0answers
55 views

Modification of Newtonian Gravity based on Maxwell's Theory

As is well-known, Maxwell's equations were already consistent with Special Theory of Relativity while the Newtonian law of Gravitation wasn't. It can be shown by solving the equations of Maxwell for a ...
1
vote
1answer
49 views

Was the pre-special relativity discussion a hot topic in the late nineteenth and early twentieth century?

We know that low-dimensional materials and topological materials are some of the current hot topics in Physics. Did this happen with the pre-special relativity discussions in the late nineteenth and ...
0
votes
0answers
32 views

Why are capacitors and inductors called that way?

I do understand that electrical resistance describes somehow the material resistance to electrons flow but I don't see the meaning behind the names capacitors and inductors (if there is any and it ...
3
votes
1answer
168 views

Electromagnetic constants and the speed of light

Was it known before Maxwell's time that the vacuum permitivity was inversely related to the permeability by a factor of $c^2$?
0
votes
0answers
75 views

Who was the first to invent the induction motor?

I have heard that Galileo Ferraris and Nikola Tesla invented the induction motor independently. Does anyone know who was the first and were they similar in power output and design? This may be a ...
4
votes
1answer
72 views

When was the electronvolt first introduced?

When was the unit "electronvolt" (eV) first introduced, and by whom? The definition of the eV requires the knowledge of the electron charge $e$, so it must have been introduced after 1909, the date ...
2
votes
1answer
151 views

Abraham's electromagnetism book and its story

Max Abraham is well known for his electromagnetic mass theory, and his book Theorie der Elektrizität is said to be read widely around 1900. I am trying to find this book, but the editions look like a ...
1
vote
0answers
287 views

Who first discovered and produced an alternating current?

What physicist first discovered or produced an alternating current and recognized it as such?
4
votes
1answer
307 views

Who discovered the magnetic vector potential, $\vec{A}$?

Neither Maxwell’s fundamental differential equations on electromagnetism nor Einstein’s first papers considered the magnetic vector potential A. So who discovered, formulated or used A for the first ...
9
votes
1answer
266 views

Why is one of Maxwell's equations named after Ampère? Who first named it after Ampère?

Ampère never wrote down what is confusingly called "Ampère's circuital law," not even the form without the displacement current term, as Ampère never dealt with the field concept.* Maxwell derived $$\...
3
votes
2answers
217 views

Why is Maxwell and not Ampère credited for unifying electricity and magnetism?

Ampère, a half century before Maxwell, theorized that magnetism was caused by electrical currents. So, why is Maxwell and not Ampère credited for unifying electricity and magnetism? (cf. the question ...
4
votes
1answer
181 views

Where in Gauss's works does he derive “Gauss's Law”?

Where in Gauss's works does he derive "Gauss's Law"? Or is "Gauss's Law" named after Gauss for a different reason?
4
votes
2answers
88 views

What was taught in 19th century European electricity and/or magnetism courses?

What topics were taught in late-19th century electricity and/or magnetism courses in Europe?
3
votes
1answer
92 views

What did Einstein learn in his university E&M courses?

What did Einstein learn in his university electricity and magnetism courses? Did he learn about such prominent results as Ampère's force law, Weber's force law derived from it (cf. Maxwell's Treatise §...
1
vote
1answer
1k views

How exactly did Hertz's experiments confirm Maxwell's theory?

Hertz's experiments are said to have proven Maxwell's theory correct, but how exactly did his experiment do this?
0
votes
0answers
24 views

Why do so many electronic equipment work on the same or close frequencies?

I know for example that one of the reasons why our cellular phones need to be turned off in airplanes is that the navigation system of the plane (GPS and other systems) works on frequencies close to ...
2
votes
2answers
202 views

How did Lorentz transformations get their modern definition?

Historically, Special Relativity was motivated by apparent inconsistencies between Maxwell's Electrodynamics and Newtonian Mechanics. In Einstein's well known paper "On the electrodynamics of moving ...
1
vote
3answers
107 views

Why make fields have momentum and energy? (or, the importance of conservation laws)

I used to get confused when I first learned the electromagnetic field is said to have a momentum. A few years later, I came across an argument for why 0.999... = 1: When faced with the task of ...
19
votes
2answers
496 views

How did scientists plot complicated graphs in the 19th century?

I am wondering how did Maxwell in the 19th century draw such figures as the one shown? What tools or procedures did he need? Is it all compass and ruler drawing?
1
vote
1answer
27 views

Origin of Textbook Argument for Displacement Current as Generalization of Ampere's Law

I was wondering where in the literature the standard textbook argument (appearing in Young and Freedman and Purcell and Morin, for example) for displacement current first appears. It seems especially ...
3
votes
2answers
978 views

Which came first, Coulomb's law or Gauss's law?

which one has been discovered earlier? Coulomb's law or Gauss's law? I've read that Gauss's law is more fundamental and of course we can derive Gauss's law using Coulomb's law and vice versa. But my ...
1
vote
0answers
103 views

Mutual induction in electromagnetic wave theory

Frequently when electromagnetic waves are taught, it is said that the change in electric field causes a change in the magnetic field, which then causes a change in the electric field, and so on and so ...
2
votes
1answer
320 views

Who discovered diamagnetism first?

Ferromagnetism is everyday life. Paramagnetism is not rare. But diamagnetism is rare and weak. So, who first discovered diamagnetism? in which material?
4
votes
0answers
120 views

How did Maxwell conclude that $\frac{\partial\bf E}{\partial t}$ was necessary to complete $c^2\nabla \times \bf B= \frac{\bf J}{\epsilon_0}\;?$

As we know $$c^2\text{curl}\;\bf B= \frac{\bf J}{\epsilon_0}$$ is incomplete & in many cases like capacitor give contradictory result against Law of conservation of charge. As Feynman writes; ...
2
votes
0answers
63 views

Historical milestones in experimental “verification” that light is a electromagnetic phenomenum

This is a follow up question to How did Maxwell conclude that light is an electromagnetic wave? where the arguments of Maxwell were explained why he considered light as an electromagnetic wave. What ...
2
votes
2answers
262 views

Wireless transmission and speed of light in Weber Electrodynamics

The telegraph model of Weber-Gauss, relying on Weber's electrodynamics, modeled instantaneous action at a distance of the electric scalar potential (Coulomb potential) manifesting as propagation of ...
10
votes
1answer
339 views

How did gyromagnetic ratio come up before quantum mechanics, and who introduced it?

I am really curious about who was the first one to define the gyromagnetic ratio $\gamma$ of a body, i.e. the ratio of its magnetic dipole momento to its angular momentum. It is a very important ...
5
votes
2answers
1k views

How did Maxwell conclude that light is an electromagnetic wave?

This is a copy of a question I just asked at Physics Stack Exchange. From reading the text on the related questions, it seems that Maxwell equated light with the carrier of electromagnetic force just ...
5
votes
1answer
5k views

Why are microwaves called “microwaves”, when they are much longer than a micrometer?

If "millimeter waves" have a wavelength of about 1 mm, one might linguistically expect microwaves to have a wavelength of about three orders of magnitude less, not the same or greater. How did ...