Electricity and magnetism Definition and 215 Threads

Electromagnetism is a branch of physics involving the study of the electromagnetic force, a type of physical interaction that occurs between electrically charged particles. The electromagnetic force is carried by electromagnetic fields composed of electric fields and magnetic fields, and it is responsible for electromagnetic radiation such as light. It is one of the four fundamental interactions (commonly called forces) in nature, together with the strong interaction, the weak interaction, and gravitation. At high energy, the weak force and electromagnetic force are unified as a single electroweak force.

Electromagnetic phenomena are defined in terms of the electromagnetic force, sometimes called the Lorentz force, which includes both electricity and magnetism as different manifestations of the same phenomenon. The electromagnetic force plays a major role in determining the internal properties of most objects encountered in daily life. The electromagnetic attraction between atomic nuclei and their orbital electrons holds atoms together. Electromagnetic forces are responsible for the chemical bonds between atoms which create molecules, and intermolecular forces. The electromagnetic force governs all chemical processes, which arise from interactions between the electrons of neighboring atoms. Electromagnetism is very widely used in modern technology, and electromagnetic theory is the basis of electric power engineering and electronics including digital technology.
There are numerous mathematical descriptions of the electromagnetic field. Most prominently, Maxwell's equations describe how electric and magnetic fields are generated and altered by each other and by charges and currents.
The theoretical implications of electromagnetism, particularly the establishment of the speed of light based on properties of the "medium" of propagation (permeability and permittivity), led to the development of special relativity by Albert Einstein in 1905.

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  1. Alex_Neof

    Infinitely long cylindrical shell (magnetic field at centre)

    Homework Statement An infinitely long hollow cylinder of radius (a) carries a constant current (i). Use Biot - Savart's law and show that the magnetic field at the centre of the cylinder is zero. Also show, using symmetry arguments and Ampere's law, the magnetic field is zero in any point...
  2. X

    Does a constant magnetic field cause a current?

    (1) I previously learned that a constant magnetic field causes a force on any electrons within its range. Clearly, this force would cause electrons to move. Isn't this creating a current? (2) However, now apparently I am told that the only varying magnetic fields can create a current. I.e...
  3. M

    Eddy currents and Torsion Pedulum

    I am having difficulties writing my damped oscillations lab report. We were asked to write a short essay on eddy currents (creation,direction advantage and disadvantage) and their relationship with torsion pendulums. Also,we have to explain if the copper wheel in the torsion pendulum could be...
  4. D

    Determining the oscillations of an electron within a sphere

    Homework Statement Using an electron as a point particle of charge −e inside a positively charged sphere of radius R ≈ 10^(−10) m and total charge +e, find the density ρ(r) of the positive charge for which the electron oscillates harmonically about the center of the sphere assuming that the...
  5. W

    Equation for the EMF generated by a spinning magnet?

    I have found an equation which gives the EMF generated in a coil when a magnet is spun near it, the equation is given as: E = FNAω × 10-8 volts. Where F is the field of the sample perpendicular to the axis of roation, N is the number of turns, A is the effective area of the coil and ω is the...
  6. Y

    Magnet/Electricity to rotate object 90 degrees?

    Hello, I want to create a motion using electricity, using the cheapest means possible (DIY). Basically I'm trying to rotate an object 90degrees when the current is on, and back to its original position when the current is off. The questions are: 1) Is this possible? 2) Can this be done using...
  7. W

    Current Loop Generating a Magnetic Field

    I'm trying to understand how to calculate the strength of the magnetic field generated by a current loop. What I know so far is: When a current moves around a loop of wire it generates a magnetic field which looks a bit like that of a solenoid, only not so concentrated through the center of...
  8. A

    Displacement Current: Difference & Example

    Is displacement current always equals to conduction current?if not then can anyone give me an example for it?if yes,then can anyone prove it?
  9. M

    Cyclotron Motion Due to Earth's Magnetic Field

    1. Say that an electron is heading towards the Earth from the sun with an initial known velocity v. And we know that at Earth's surface the magnetic field is given by B1. This B varies as (R1/R2)^2 where R1 is the radius of the earth. How can I find the location in space, R3/R1, where R3 is the...
  10. W

    Viable Railgun Setup? (ping pong balls)

    Hello, I'm working on a personal project that requires a very precise, but not very powerful, ping pong ball launcher. Would it be possible to coat a ball in metallic conductive paint, and then fire it from two rails like a railgun? Would I still get a constant net force in the correct...
  11. M

    Why Does Rearranging an Inductor Yield Different Magnetic Fields?

    I found two ways to solve this problem, but I get two different solutions, it's confusing because I can't see the flaw in wrong solution. 1. Homework Statement Long cylindrical inductor of diameter D1 and inductance L1 is connected to battery and creates magnetic field B1. Inductor is then...
  12. N

    What Causes Magnetism and Repulsion in Magnets?

    When you take two magnets one being positive, the other negative. What is the chemical makeup of these two magnets that makes them repel each other. And if I have this correct, electricity is caused by magnet coils spinning around which generates electricity. What is it about magnets (especially...
  13. Hijaz Aslam

    Force on a circular loop due to hypothetical magnetic field.

    Homework Statement A hypothetical magnetic field existing in a region is given by ##\vec{B}=B_o\vec{e}_r##, where ##\vec{e}_r## denotes the unit vector along the radial direction. A circular loop of radius a, carrying a current ##i##, is placed with its plane parallel to the X-Y plane and the...
  14. W

    Engineering Tough Circuit Problem, Find Current When Switch is Closed

    Homework Statement I got questions a) and b), but I'm stuck at c) and d). Homework Equations Kirchhoff's Loop and Junction rules. Equivalent resistance in series: Req = R1 + R2 Equivalent resistance in parallel: Req = ((R1)-1 + (R2)-1)-1 The Attempt at a Solution I really haven't gotten...
  15. S

    Slab of material in magnetic field. Determine magnetic field

    Homework Statement A very large slab of material of thickness d lies perpendicularly to a uniform magnetic field \vec H_0 = \vec a_zH_0, where \vec a_z is the unit vector in the z-direction. Determine the magnetic field intensity (ignoring edge effect) in the slab: a) if the slab material...
  16. A

    Electromagnet with high remanence

    I am in search of an electromagnet which has high magnetic remanence (or retentivity) even when the current through the electromagnet is zero. Can someone provide information about such a material?
  17. 2

    Force between two parallel wires carrying current?

    There is something I am confused about when it comes to the force between two parallel wires carrying current, specifically why when they carry current in the same direction the wires are attracted to each other. I understand that when you use Flemming's left hand rule and consider the electrons...
  18. M

    Electricity and Magnetism Project

    Hello everyone. For this semester's laboratory, we are required to work on a project on the topic of E&M (preferably). They've given us freedom of choice as to what we want to work on and I was wondering if any of you guys know some interesting and cool topic we (me and my partner) can study...
  19. Alxb577

    Electromagnetics Essay Topic Ideas

    Hi Everyone, I need to write an essay for my electromagnetism class and i was wondering if anyone has good topic ideas. My criteria is that it needs to be 10 pages and I would like something that is interesting for me to research and write about. I was thinking so far of magnetic levitation...
  20. D

    What is your proposed list of experiences for a Physics II (Electricity and Magnetism) laboratory?

    I'm a new TA in a physics laboratory and we're going to redesign experiences for fundamental physics II lab that is a semester course on electricity and magnetism for undergraduates in their 2nd year. What is your proposed list of experiences for a Physics II (Electricity and Magnetism)...
  21. B

    Differential form of gauss's law.

    I don't understand what charge density is meant in the equation: div E = constant times charge density. I have the derivation in front of me and the last step follows from accepting that the rate of change of the integral of the field divergence per change in volume is the same as the rate of...
  22. davidbenari

    Total energy in a system of capacitors

    Can someone provide for me a proof that the total energy of my equivalent capacitor is equal to the sum of the energy in all capacitors? Or, if this is untrue, tell me why? Is this applicable to current and resistors too? Thanks a lot.
  23. E

    Electricity and Magnetism Workbook

    Hello everyone. I am searching for a book full of practice problems in Electricity and Magnetism and was hoping someone could recommend some. I have been searching on my own, but could not find any. I have a classmate who has one from china, where it is pure questions relating to the subject and...
  24. R

    Can a Charged Particle Move in a Straight Line in a Nonzero Magnetic Field?

    Homework Statement A charged particle moves in a straight line through a particular region of space. Could there be a nonzero magnetic field in this region? In either case, include a sketch as well as prose in your justification. Homework Equations The Attempt at a Solution The...
  25. bcrowell

    Free edition of Purcell, Electricity and Magnetism

    Thirty years after learning E&M from the wonderful book by Purcell, I noticed that the copyright page of my dog-eared copy of the 1965 edition includes a notice stating that it is available for use by authors and publishers on a royalty-free basis after 1970. The book has gone through two more...
  26. K

    How Is Electricity and Magnetism Used In Computer Science?

    I am a computer science major and we are required to take two semesters of physics. First semester is based on mechanics and the second semester is focused on electricity and magnetism. I was wondering how these topics are used in computer science and in what specific area? I have tried looking...
  27. D

    Does Work Done by a Spherical Force Field Depend on Path?

    Homework Statement A force eld E has the spherical components Er = (2Dcosθ)/r3 Eθ = (Dsinθ)/r3 E\phi = 0: (a) Evaluate by line integration the work it does in taking a point (parti- cle) from point A in the diagram to point B via the quarter circle r = a; 0 <...
  28. T

    Relationship electricity and magnetism

    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...
  29. Newtons Apple

    Exploring the Significance of Coils in Electricity and Magnetism

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  30. M

    Which Physics Book on Electricity and Magnetism Explains Concepts in Vectors?

    Can someone recommend a physics book on electricity and magnetism? The book that I just finished reading for my class was https://www.amazon.com/dp/0971313458/?tag=pfamazon01-20 The book above hardley mentioned vectors and I am looking for a book that explains all the concepts in terms of...
  31. K

    Schools Why do the collegeboard offer Electricity and Magnetism?

    If a prerequisite for E&M is Multivariable calculus, why is it offered in high school (without that pre-req)? Is the High School E&M equivalent to physics 2 in college, and if that is so, Physics 2 is still offered before Multivariate calculus. Can someone clear this up for me. Am I getting two...
  32. I

    Good study guide for Electricity and Magnetism?

    I wasn't really sure where to post this, but I am currently taking a second year Electricity and Magnetism course this term. I want to be able to do well in this course in order to keep my GPA up, but I don't have a particular interest in this class and the prof flies through the material at a...
  33. C

    Electricity and magnetism ( word problems )

    Homework Statement please cheack my answears and see if they are right, please help me solve the wrong ones thankyou ! (1)if you were to expend 10 J of work to push a 1 C charge against an electric field , what would be its change of Voltage ? voltage = electric potential energy /...
  34. bcrowell

    Classical Electricity and Magnetism by Edward Purcell

    Author: Edward Purcell Title: Electricity and Magnetism Amazon Link: https://www.amazon.com/dp/1107013607/?tag=pfamazon01-20 Prerequisities: Freshman mechanics. A year of calculus. Purcell introduces vector calculus from scratch, but most students who hadn't already had vector calc would...
  35. N

    Is taking Electricity and Magnetism without Mechanical Physics a difficult task?

    Hey. So I switched from ChemE to Engineering-physics (I guess I followed my hearth here, instead of my head), and this entails I will have to take a course in Electricity and Magnetism this semester. During the previous one, the Engineering-physics guys took a course in mechanical physics, and...
  36. D

    Electricity and magnetism confusion

    Homework Statement I've been set an assignment and I'm struggling with one question in particular: Homework Equations 'Use the following data and plot the graphs for a point charge' 'Plot graph of E against r^2. Interpret the graph to describe electric field strength and electric...
  37. denjay

    What makes Electricity and Magnetism a unified force?

    What makes Electricity and Magnetism a "unified" force? I'm taking upper level Electromagnetism and we've dealt with the various formulas dealing with electricity and magnetism. It seems to me that we are still largely dealing with them separately. In that, I mean we have a thing called a...
  38. H

    What is the deal with kinetic and potential energy, electricity and magnetism

    Hello, Firstly i am new here ( not offering an excuse) and an on and off lurker to this awesome forum. I am trying my best to fit into the established rules ,sorry if i broke any inadvertently. If kinetic and potential energy represent the same things why are there entities representing the...
  39. B

    Textbook for junior level electricity and magnetism

    Since the instructor of my course doesn't use a textbook and just teaches based off his notes, what would be a good text to supplement my learning (when asked what he recomends, he just said find something in the library). Does electrodynamics = electricty and magnetism? I've heard this one is...
  40. L

    Preparing for Electricity and Magnetism (advanced, undergraduate level)

    Hello PF, I am a few weeks from starting my second year as an undergraduate. This fall I will be taking the Electricity and Magnetism course for physics majors (crosslisted for graduate students). Last spring I took the introductory physics course on electrostatics and magnetostatics. The...
  41. S

    How Does Current in a Wire Create a Magnetic Field?

    hi , i wanted to ask why does current in a wire produces a magnetic field ? and can anyone explain how maxwell related electricity and magnetism , easily (im in high school)
  42. S

    Electricity and magnetism (magnitude of magnetic field)

    A 1000-turn toroidal solenoid has a central radius of 4.2 cm and is carrying a current of 1.7 A. What is the magnitude of the magnetic field inside the solenoid at the central radius? (μ0=4∏×10^-7 T ∙ m/A) r= 4.2cm= 0.042m B=(μ0)(I)/(2∏)(r) ⇔ (4∏×10^-7)(1.7)/(2∏)(0.042) ⇔ 1.43x10^-8 T? Or...
  43. S

    Electricity and magnetism (magnitude of current flowing)

    If the area of a tube is 0.0000283 m, with moving ions contributing to a magnetic field of 44.0x10^-4 T. What is the current flowing through the tube? [permeability of free space 'mu subzero'= 4∏x10^-4]. I don't have a clue of how to start attacking this problem, have a genius professor, but...
  44. C

    Studying Self Studying AP Physics C: Electricity and Magnetism

    No, you didn't read the title wrong. I am really self studying a physics class. I just finished Mechanics (Physics I) and since I want to go to college to study physics to become an engineer or physicist. I need to take the next class, E&M (Physics II, Electricity and Magnetism). However, I...
  45. TheTank

    Thinking about electricity and magnetism, and some relativity

    I have 2 questions. I have been thinking about these two things a while, and got no one to ask, so hope to get some info/answeres here:) 1: When an electron is standing still, it produces an electric field (and no magnetic field), right? So when many electrons is moving with a constant...
  46. E

    New animated video on Electricity and Magnetism

    I have just created a short animated video explaining all the concepts of electromagnetism. It is at: http://youtu.be/XiHVe8U5PhU I put a lot of of time and effort into making the animations, so please take a look at this, and please pass it along to anyone who you think might be...
  47. D

    How to Find the Voltage Across a Capacitor in an RLC Circuit?

    My question is how do I find the voltage across a capacitor? I have an RLC circuit with a switch and battery. It only gives me the values for the battery, L, C, and R. My main question is, is there an equation or something to find the voltage across a capacitor?
  48. D

    Calculus vs. algebra based phyics 2 (electricity and magnetism)

    I am a biochemistry major and I need to take the first two introductory physics courses as a prerequisite to physical chemistry. I can take regular pchem, which requires calculus based physics or pchem for biochemists, which only requires the algebra based physics. With the way my university...
  49. R

    Electricity and magnetism point charges problem

    Homework Statement Four point charges have equal magnitudes. three are positive and one is negative, as the diagram shows. they are fixed in place on the same straight line, and adjacent charges are equally separated by a distance d. consider the net electrostatic force acting on each...
  50. G

    Which Way Is V? Understanding the Relationship Between Electricity and Magnetism

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