Electromagnetism Articles

Tag Archive for: electromagnetism

Milli-Ohm

The Poor Man’s Milli-Ohm Meter

/
0 Comments
Introduction In a previous article on measuring battery internal resistance, a simple technique for low-resistance measurement was outlined. In this article,…
gauss law misconceptions

A Physics Misconception with Gauss’ Law

/
3 Comments
Introduction It is relatively common to see the following type of argument: The surface area is ##A## and the enclosed charge is ##Q##. The electric…
model magnet

How to Model a Magnet Falling Through a Conducting Pipe

/
7 Comments
Introduction In an earlier article, we examined a magnet falling through a solenoid. We argued that the point dipole model can account for the basic features…
model magnet

How to Model a Magnet Falling Through a Solenoid

/
11 Comments
Introduction Modeling a magnet realistically is a task best done numerically.  Even the simplified model of two separated disks with uniform surface…
magnetism current

Symmetry Arguments and the Infinite Wire with a Current

/
0 Comments
Many people reading this will be familiar with symmetry arguments related to the use of Gauss law. Finding the electric field around a spherically symmetric…
electromagnetic computations duality

Building a Numerical FEM Solver for Duality in EM Fields

/
0 Comments
In the previous insights article (How to Use Duality in Computational Electromagnetic Problems), I covered some uniqueness theorems for the Riemann-Silberstein…
electromagnetic computations

How to Use Duality in Computational Electromagnetic Problems

/
1 Comment
Some weeks ago I happened across a post that caught my eye. Dale asked a question about the number of photons in an electromagnetic field. His question…
Split Electric Fields

Es vs Em Fields in Electrodynamics: Capacitor & Antenna

/
0 Comments
Abstract The analysis of the two kinds of electric fields, namely the irrotational and non-conservative, is extended to electrodynamics, as exemplified…
electromagentic waves traverse

Are Electromagnetic Waves Always Transverse? Full Explanation

/
5 Comments
Electromagnetic (EM) waves are always transverse in the weak sense: the electric field (E) and magnetic field (B) are always perpendicular to the direction…

How to Recognize Split Electric Fields

/
1 Comment
Introduction In a previous Insight, A New Interpretation of Dr. Walter Lewin’s Paradox, I introduced the fact that there are two kinds of E fields. …
DC straight wire

Relativistic Treatment of the DC Conducting Straight Wire

/
11 Comments
Introduction The direct-current-conducting infinitely long wire is often discussed in the context of relativistic electrodynamics. It is of course a completely…
maxwell magneto

Maxwell’s Equations in Magnetostatics and Solving with the Curl Operator

/
0 Comments
Introduction: Maxwell's equation in differential form ## \nabla \times \vec{B}=\mu_o \vec{J}_{total}+\mu_o \epsilon_o \dot{\vec{E}}  ##  with ## \dot{\vec{E}}=0…
What is the double split

What is the Double Slit? A 5 Minute Introduction

/
0 Comments
Definition/Summary The double-slit is a simple configuration used to demonstrate interference effects in waves.Equations At distances that are…
Magnetic Field Lines

Are Magnetic Field Lines Real?

/
31 Comments
Introduction We recently had a question in the relativity forums that mentioned the behavior of magnetic field lines and reminded me of my confusion at…
walter lewin

Lewin’s Circuit Paradox: Distinguishing E_s and E_m

/
65 Comments
Introduction Much has lately been said regarding this paradox that first appeared in one of W. Lewin's MIT lecture series on YouTube (see References [1]).…
magnet

Permanent Magnets Explained by Magnetic Surface Currents

/
38 Comments
Introduction: The purpose of this Insight is to explain permanent magnets in a way that is in agreement with advanced textbooks on the subject, and that…
acusticbeats

Mathematics of Acoustic Beats: Explanation & Examples

/
11 Comments
Introduction Purpose and scope In late high school physics courses and first-year university courses, the phenomenon of acoustical 'beats' (digital audio)…
electrostaticfield1

Learn About Energy Gained by Charge in an Electrostatic Field

/
2 Comments
Energy gain of an electron in a potential V I have seen this question being asked frequently on here. A lot of students have a bit of an issue in understanding…
electrical wire

Mutual Inductance: When k≠1 and Two Coupling Coefficients

/
4 Comments
Mutual inductance and the coupling coefficient A commonly used formula for mutual inductance M between two nearby coils L1 and L2 is M = k√(L1*L2).…