# electromagnatism

1. ### How can I increase the wavelength of light photons?

Summary:: need to increase the wavelength of light. I am an intro physics student working on a project and need to increase the wavelength of photons. I only have visible light sources available but need to have an emission of a wavelength larger than 1mm. is there a way to shift wavelength...
2. ### Studying What's the best way to apply the concepts learned in physics 2?

I'm finishing up physics 2(intro E&M) at my college, and I'd like to apply the concepts I learned in it over the summer. I was considering working through an electronics book, or building a radio, etc. What kind of projects or books do you recommend to cement some of the topics I learned in a...
3. ### Is there any evolutionary benefit from magnetoreception?

Some organisms still have magnetoreceptors, what would be the evolutionary benefits of these receptors?
4. ### Average electric field over a spherical surface

1. Homework Statement I was working out problem 4, chapter 3 of Introduction to Electrodynamics by Griffiths: a) Show that the average electric field over a spherical surface, due to charges outside the sphere, is the same as the field at the centre. b) What is the average due to charges...
5. ### What is the magnetic field generated by these two particle beams?

A uniform beam of positively charged particles is moving with a constant velocity parallel to another beam of negatively charged particles moving with the same velocity but in opposite direction separated by a distance d. Then, how should be the variation of magnetic field B along a...
6. ### I Significant Physical/Chemical Change Found by Sign Reversal?

We know that "plastic" and "glass" charges were arbitrarily assigned to be negative and positive respectively, and electrons and protons were given their charges based upon that assignment (According to Randall D. Knight in Physics for Scientists and Engineers). I am curious if any significant...
7. ### A Quantization of the electric field inside a box

Hello all, The second quantization of a general electromagnetic field assumes the energy density integration to be performed inside a box in 3D space. Someone mentioned to me recently that the physical significance of the actual volume used is that it should be chosen based on the detector used...
8. ### Deflection of wave in dissipative media with a complex refractive index

1. Homework Statement A monochromatic plane wave with wavelength 500µm is propagating through a dissipative medium with refractive index 1-0.0002i. It approaching the edge of the medium, and will pass out into free space. If the angle of incidence is not 90°, how much will the wave deflect as...
9. ### I What math topics should one master for first year physics?

I’ll be taking the year long physics sequence at my college this fall and I want to know what specific math topics I should master, so that I can conquer my first year of physics. I’m planning to brush-up on any necessary topics from algebra, through precalc, and including calc 1. It’s an honors...
10. ### I Poynting vector - uniform vs accelerated charge

I am trying to understand why an accelerating charge emits radiation/electromagnetic waves but a uniformly moving one does not. I saw one video on Youtube where it seemed that it was explained by the fact that with a uniformly moving charge the Poynting vector was pointing 'in to the volume' -...
11. ### I Do hot objects always glow?

I'm talking hotter than T = 6000k. The higher the temperature, the more the curve in the attached figure would shift to the left (while at the same time getting higher). So the intensity peak would eventually fall back into the invisible portion (very small wavelength this time) of the...
12. ### A Jump conditions for electric field across an interface

Hi, I have some confusion about the jump conditions for an electric field across an interface between two materials with different properties. In general, we have the two jump conditions across an interface: n.(ɛE)+ - n.(ɛE)- = σ...
13. ### Plasma ball electric shock mystery

Plasma ball has a high voltage. Why don't we get an electric shock when we touch it?
14. ### How to calculate total cross section from differential cross section

I was doing the calculations for this: http://fermi.la.asu.edu/PHY531/cylinder/index.html But I can't figure out how to go from \frac{d\sigma}{d\phi} to the total cross section. My guess was that you did the integral from \phi=0 to \phi=2\pi, but that's not helping since I can't tell either how...
15. ### Energy of a solenoid with a partially removed core

1. Homework Statement A solenoid of volume V, current I and n turns per unit length has an LIH core, relative permitivity is \mu_r. This core is then slid out so that a fraction f of the solenoid's length is filled with air/vacuum (and 1-f is filled with the core). Neglecting hysteresis...

It is a well known fact that, in electromagnetic units, strength of a shell and strength of current flowing through its boundary are same. See here. $$\begin{matrix} \text{i.e.}\: i \text{(biot)} = \phi \text{(biot) } \end{matrix} \tag{1}$$ (a) While converting to...
17. ### I Correct relation is F^{ij} = - epsilon^{ijk} B^k.

When I tried to derive this relation I got the wrong sign. Please check the pic and tell me my mistakes.
18. ### I How do I apply Maxwell's equations?

For example, if I have a magnetic field perpendicular to some surface and I change this magnetic field with constant speed, how do I calculate the Electric field at any point on this surface, since ∫E⋅ds=k, where k is some constant, could be done with many different vector fields.

26. ### What is the value of induced magnetic field?

1. Homework Statement Two coencenteric metalic shell has inner radius $r_1$ outer radius $r_2$. We place along axis infinity wire has $\lambda$ charge in per unit length. The inner region of metalic shells inserted with relative permabilitty coefficent $\epsilon$. This system rotates with...
27. ### Current and magnetic field in a spherical capacitor

<< Mentor Note -- Thread moved from the technical forums,. so no HH Template is shown >> Hello! I have a question on Electromagnetics. Could anyone check if I am on the right track? Here is the proposed problem: Consider a spherically symmetric current distribution, which is radial and...
28. ### I How to convert movemnt/speed to electricity or other E.forms

Hi I was wondering if there is a way to produce energy using the movement of vehicles on the road. I do not know which principles can come into picture, but I believe Electromagnetism/ detection is the way to go? If someone could at least throw me in the right direction of which field to...
29. ### Energy and momentum imparted by an EM wave

1. Homework Statement A plane electromagnetic wave is incident on a material surface. The wave delivers a momentum $p$ and energy $E$. Then which of the following is/are correct? 1) $p=0,~E=0$ 2) $p\neq 0,~E=0$ 3) $p=0,~E\neq 0$ 4) $p\neq 0,~E\neq 0$ 2. Homework Equations None...
30. ### Potential of a Rectangular Pipe by Laplace's Equation

1. Homework Statement 2. Homework Equations Is my part a correct and am I on the right track for part b? If not please give me some suggestions to get me closer to the right track. Also, how would I even begin c.? We have literally done no examples like this in class. 3. The Attempt at a...