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.

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How did Weyl's 1918 paper; Gravitation and Electricity, influence classical physics?

The main-stream view seems to be that Weyl's 1918 paper Gravitation and Electricity was initially considered a failure for reasons first pointed out by Einstein. But these initial ideas were reapplied ...
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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; ...
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170 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 ...
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108 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 ...
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120 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 ...
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64 views

de Broglie's conception of the electron

I've been working on de Broglie's thesis (English PDF, Original French PDF) for a course, and I've found something that's been bothering me. My training is in Physics, and so I'm not particularly ...
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22 views

Who invented the quadrupole lens for charged particles?

I am wondering who actually invented the (magnetic) quadrupole lens or who used it for the first time. I have found some papers from the 50s and 60s about more complicated systems based on Quadrupoles,...
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43 views

Who originally worked out the magnetic field produced by a solenoid and toroid?

Although, it seems very easy to find the magnetic field produced by a solenoid or a toroid, all we got to do is to make a suitable an Amperian Loop and take the $\mathbf B$ out of the integral and so ...
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105 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 ...
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47 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 ...
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194 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 ...
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70 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 ...
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84 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 ...
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72 views

Validity of Maxwell's equations in the aether's reference frame

If Maxwell's equations were experimentally found on Earth such as Faradays law, coulombs law , and worked in the Earth's frame of reference, then why did people believe them to be valid in the aether'...
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30 views

What is a Heaviside rational current element?

This terminology seems to be referred to a notion invented in an old book of Oliver Heaviside [1]. What is it and why the Biot-Savart law is not unique unless it is applied to a Heaviside rational ...
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45 views

How and for what purpose did Lorentz come out with his "electron model"?

Who suggested to him the idea that charge wasn't really some excess or defect of "electric fluid", but rather something carried by a particle?
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97 views

Are there any descriptions of the reluctance motor invented by W.H. Taylor in the 1800's?

I could not find any descriptions of the first motors of W. H. Taylor in Wikipedia of any reference, history or circumstances surrounding its invention. Apparently the motor was never used for any ...
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63 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 ...
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115 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 ...
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644 views

Who first discovered and produced an alternating current?

What physicist first discovered or produced an alternating current and recognized it as such?
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162 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 ...
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1answer
64 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 ...
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1answer
486 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 ...
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54 views

How did Gauss, Ampere and Biot-Savart derive their laws?

Gauss' law for electricity and magnetism, Ampere's law and Biot-Savart's law — all of these laws are crucial for understanding electromagnetism and Maxwell's equations. But I want to know how each of ...
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69 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 ...
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46 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 ...
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63 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 ...
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408 views

Are Gauss' electrodynamics laws for charge-charge interaction correct at all?

My question refers to a fragment on electrodynamics written by Gauss at around 1835. In this short note (see Gauss' Werke, volume V, p.617) Gauss wrote down a fundamental equation which describes the ...
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42 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 ...
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140 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 ...
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31 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 ...