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 and magnetism were considered to be two separate forces. This view changed with the publication of James Clerk Maxwell's treatise on electricity and magnetism.

Filter by
Sorted by
Tagged with
2
votes
1answer
113 views

Was it suspected that electric signals traveled at the speed of light?

Was it believed early on that signals sent via wire moved at exactly the speed of light or simply very fast? Who was the first to estimate the speed? EDIT: Given that they move at less than the ...
2
votes
1answer
52 views

When was spin of subatomic particles other than the electron discovered?

The idea of a spin angular momentum was first proposed in a 1925 publication by George Uhlenbeck and Samuel Goudsmit to explain hyperfine splitting in atomic spectra. At what time was it measured ...
8
votes
1answer
471 views

Historical origin of magnetic monopoles

There are two related historical questions that I'm trying to find answers to: Who was the first to introduce the concept of magnetic monopoles? Griffiths in his textbook Introduction to ...
0
votes
0answers
35 views

How did Gauss and Lagrange derive Gauss law of Electrostatics

On Wikipedia, these two pages are mentioned :Lagrange and Gauss however I am an English speaker and can not comprehend any of the one, can someone provide the translated pages or shortly their line of ...
2
votes
1answer
55 views

What is Leroy Grumman Medal won by theoretical physicist Kenneth G. Wilson?

I happened to find that one of the most important inventors of the renormalization group, Kenneth G. Wilson, won the Leroy Randle Grumman Award Medal in 1986, 4 years after his Nobel prize. Details in ...
2
votes
1answer
77 views

How was (non-instantaneous) electric current first discovered?

How was (non-instantaneous) electric current first discovered and what were some of the main first thoughts on it?
4
votes
0answers
65 views

When was the ratio between electric and magnetic forces in an electromagnetic field established?

We know that the magnetic force on a particle moving in a magnetic field was found by J.J. Thomson in 1881, with a slight mistake, and then corrected by Heaviside in 1885 to $F_M = q\,v\times B$. Can ...
2
votes
1answer
132 views

What was the real need of divergence and curl operators?

As I'm advancing my study in Electromagnetism I'm getting introduced to more mathematical operators which are exclusively used in Electromagnetism and Fluid Dynamics only. Let me try to explain ...
2
votes
0answers
97 views

Feynman's statement about the importance of basic science

I remember reading in the line that Feynman saying if the best technicians were tasked to build a radio they would make longer and thicker cables and transfer message but it took a physicist to ...
5
votes
1answer
82 views

Did the principles of celestial mechanics affect the development of electromagnetism?

Much of the early theoretical work in electricity and magnetism appears to have been the result of applying celestial mechanical principles to electrostatics. Examples include Cavendish's inverse-...
2
votes
1answer
141 views

What is the idea behind Maxwell's “displacement current” in electromagnetism?

I'd like to get an explanation why Maxwell chose the name "displacement current" for the term $\mu_0\epsilon_0\frac{\partial E}{\partial t}$ he added to Ampere's law (Maxwell's correction). I'm ...
2
votes
0answers
27 views

Difference between Perrin's and J. J. Thomson's experiment

In J. J. Thomson's paper (Phil. Mag. S. 5. Vol. 44. No. 269. Oct. 1897) concerned with cathode rays, Thomson writes, that the experiment by Perrin that supposedly proves that cathode rays are made of ...
2
votes
0answers
122 views

Who discovered Maxwell-Faraday equation, $\nabla\times E=-\frac{\partial B}{\partial t}$? Was it Maxwell or Neumann?

I have been trying to find out who discovered Maxwell-Faraday equation, $\nabla\times E=-\frac{\partial B}{\partial t}$. Was it Maxwell himself, or was it Franz Ernst Neumann who derived it? The ...
5
votes
2answers
178 views

How did Henry Cavendish deduce the inverse square law in electrostatics from his experiment in 1772?

An elegant experiment in 1772 by Henry Cavendish. Cavendish charged a spherical conducting shell that contained within it, and temporarily connected to it, a smaller sphere. The outer shell was then ...
3
votes
1answer
342 views

How was it discovered in the 19th century that electric or magnetic forces were not instantaneous?

Marc Lange writes (page 29) It was known by about the 19th century that any action at a distance involving electric or magnetic forces would be retarded and so undermine not only spatial locality, ...
2
votes
0answers
55 views

Who introduced concept of capacitance matrix

We know of two ways of representing voltage-charge relations of an assembly of conductors: $V_j=\sum P_iq_i$ and $Q_j=\sum C_iv_i$ Who introduced these equations for the first time and though one can ...
2
votes
1answer
209 views

Origin of the Heaviside function?

I have tried to find the actual origin of the Heaviside unit step function and could not. I've searched and searched, read one complete biography of Oliver Heaviside, skimmed another, but nowhere can ...
0
votes
1answer
192 views

Why is electric dipole moment represented by “p”?

"I recently came across a text where the electric dipole moment was represented as "d" instead of the more commonly used "p". The reason behind using "d" here is probably that "dipole moment" begins ...
0
votes
1answer
122 views

How on Earth did Ampere come up with Ampere's circuital law?

When I asked for proof of Ampere's circuital law I learned that this law itself is taken as an axiom. Okay I just need to know how did he come up with such a law? how to confirm that result ...
4
votes
1answer
105 views

High voltage / current sources in 19th century cathode ray experiments

In modern chemistry textbooks, a DC source (battery symbol) is usually shown for cathode ray tube experiments by Thomson and others. Certainly, no battery can provide very high voltages needed for gas ...
3
votes
2answers
747 views

Did Maxwell originally write his equations using quaternions?

I read somewhere, some time ago that Maxwell originally wrote his eponymous equations using the formalism of quaternions and it was only the later intervention of Gibbs and Heaviside that put them ...
1
vote
1answer
64 views

Charge concept before discovery of electron [duplicate]

How did the concept of positive and negative charge originate before the discovery of an electron? My question is related to the historical aspects.
3
votes
1answer
82 views

What were the 3 critical experiments and the argument given by Ampère which helped in determining the magnetic field made by electric current?

In The Feynman Lectures on Physics volume 2, Magnetostatics, section 13-4 Mr. Feynman tells us that there were "three critical experiments and a brilliant theoretical argument given by Ampère" that ...
0
votes
0answers
43 views

How did Reginald Fessenden realize that spark-gaps could generate waves and the modulation of those waves with voice?

I can somewhat understand how the spark-gap was devised to transmit waves and how the waves were first measured in frequency but what lead to the idea of "modulation" where another electrical signal ...
1
vote
1answer
447 views

How did people measure electric charge at the time of Coulomb?

Around the time that Coulomb gave Coulomb's law, how did people measure electric charge?
1
vote
2answers
211 views

Who discovered Bremsstrahlung?

I found a web page that says that it was discovered by Tesla in 1890, is that true or generally acknowledged? Isn't 1890 too early a date?
9
votes
4answers
227 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
52 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
58 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
256 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 ...
6
votes
2answers
246 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 ...
3
votes
1answer
276 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
282 views

Is Gauss's electrodynamics law for inertial motion correct at all?

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 ...
4
votes
3answers
94 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
59 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
1answer
79 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
838 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
36 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
222 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 ...
4
votes
0answers
93 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
314 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
257 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 that two of the many reasons might be ...
4
votes
1answer
76 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
79 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
57 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 ...
4
votes
3answers
429 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 ...
1
vote
0answers
91 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
58 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
38 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
242 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 $c^2$?