Fields Definition and 1000 Threads

Hi, We know that a varying magnetic field creates and induced electric field, and a varying electric field creates an induced magnetic field. If there is a varying electric field (let's say sinusoidal), then this electric field creates an induced magnetic field. And if this produced magnetic...

It's an MCQ, and I chose 4/81 v(esc). Is this correct? There isn't a marking scheme... :cry:

Wanted to check with you guys that I'm not going crazy... Exercise 19: Let ##\phi : \mathbf{R}^2 \rightarrow \mathbf{R}^2## be a counterclockwise rotation by angle ##\theta##. Let ##\partial_x, \partial_y## be the coordinate vector fields on ##\mathbf{R}^2##. Show, at any point of...

I'm not sure the following passage is so trivial as it was supposed to be: I mean, what does exactly prove it? That's my question. The step is the following: if ##P## has a root ##\alpha## in ##\mathbf L## - an extension of ##\mathbf K## of degree <= ##\frac n 2## where n is the degree of ##P##...

Hello, I am ready to apply to grad schools and would like to have a few insurance schools just in case. What are the easiest physics fields (biophysics,nuclear physics...etc) to get into a PhD for? Regards,

I was wondering -- does a magnetic field repel or attract electrons ? Also when you place two magnets together with the same polarity and you feel that pressure - what is this called and can protons or electrons pass through this field -- thanks for the help

Hi all! I was wondering, Is it possible, given a specific dipolar molecule, to create the perfect oscillating electric field so as to heat it and not, i.e. the water around it? What I'm basically asking is could there exist a specific microwave just for X and not all dipolar molecules without...

(I am not sure which forum this post belongs to. Hope someone kindly helps me move it to a proper forum.) In papers, for example, here, here, and here, the authors start from the Lagrangian for matters and gravitational fields, then Dirac's constrained canonical quantization is used. They...

I cannot seem to start answering the question as a result of the path not being provided. How do I solve this when the path is not provided? See picture below

Hi there. I'm trying to solve the problem mentioned above, the thing is I'm truly lost and I don't know how to start solving this problem. Sorry if I don't have a concrete attempt at a solution. How do I derive the Feynman rules for this Lagrangian? What I think happens is that in momentum...

Hello , what quantum fields exist in intergalactic space ? What math describes these fields ?

Summary:: I have an idea for a sci-fi story in which something like a headband or electrodes in the brain could be used for augmented reality. Could such devices work physically? This might be partially in the realm of neuroscience, but could a headband create a pinpointed magnetic field (in...

I don't have access to high power systems, or ultra precise detectors.(around 10V/ 1A) Can I detect small variations (frequencies ?) of magnetic field, while ignoring the noise caused by the Earth's magnetic field ? My goal is to measure the magnetic field through a line in order to trace it...

I'm having trouble with Rovelli's new book, partly because the info in it is pretty condensed, but also because his subjects are often very different from those in other books on GR like the one by Schutz. For one thing, he never uses the term "manifold", but talks about frame fields, which seem...

I am wondering if the phase diagram of Carbon has been explored at very large electric fields. Can one make any theoretical guesses ? In specific I am interested in Pressure Vs Electric field and Electric field vs Temperature at fixed temperature and pressure respectively.

Magnetic fields coupling question. I had to make a small tool holder for my drill press, it hangs on side of press using N52 cylinder magnets. The holder is 4" long x 3/4 x 3/4" AL bar. With a spacing of 3", two 1/2" holes are bored to accept the 1/2 x 1/2 N52's, which will be epoxied in. I...

Magnetic fields as an alternative explanation for the rotation curves of spiral galaxies ABSTRACT THE flat rotation curves of spiral galaxies are usually regarded as the most convincing evidence for dark matter. The assumption that gravity alone is responsible for the motion of gas beyond the...

If I'm standing on Earth, is my time dilation actually greater than if I was in a rocket accelerating at 9.8m/s^2 in deep space due to me being in a gravitational field on top of the acceleration? Geodesics experience time dilation in gravitational fields, so it seems like there is an additive...

Hello everyone. I have been recently working in an optimization model in the presence of uncertainty. I have read https://www.researchgate.net/publication/310742108_Efficient_Simulation_of_Stationary_Multivariate_Gaussian_Random_Fields_with_Given_Cross-Covariance in which, a methodology for...

I bought an EMF meter that can discriminate to electric fields, and it is highly sensitive to the proximity of my body. What is it in the human body that emits electric fields? Is it muscle activity? Maybe many things in the body? Thanks.

The given diagram looks something like this: Electric force on nucleus from external field must balance attraction force from electron cloud and electric force from external field. $$e\vec{E}=\frac{k(\frac{L^3}{R^3}e)}{L^2}\hat{L}$$ where ##\vec{L}## is from center of electron cloud to...

Apostol defines limit for vector fields as > ##\quad \lim _{x \rightarrow a} f(x)=b \quad(\rm or\; f(x) \rightarrow b## as ##x \rightarrow a)## means that : ##\lim _{\|x-a\| \rightarrow 0}\|f(x)-b\|=0## Can't we say it's equivalent to ##\lim _{x \rightarrow a}(f(x)-b)=0##

For example, $$\left\langle \frac x {r^3}, \frac y {r^3} \right\rangle = \nabla \left( -\frac 1 r \right)$$ where ##r=\sqrt{x^2+y^2}##, is a gradient field even though it is undefined at the origion. I get that it is physically possible since it is similar to the equation of the electric field...

Need help with part iii) i) Under ##C \rightarrow C + d\Lambda##, and since ##dG = d^2C = 0 \implies d(\Lambda \wedge G \wedge G) = d\Lambda \wedge G \wedge G##, then neglecting the surface terms\begin{align*} \int_D d\Lambda \wedge G \wedge G = \int_D d(\Lambda \wedge G \wedge G) &=...

Let’s start things off straight: I LOVE physics. I love the opportunity to understand the world more in depth and mathematically and have had good experiences with all my professors in all of my classes. I have loved the teaching experience I have had as a several-time TA, as well as the deeper...

relevant eduation

Consider a region where a 25-volt-per-meter electric field and a 15-millitesla magnetic field exist and are along the same direction. If the electron is in the said region, is moving at a direction 20 degrees counter-clockwise from the direction of the magnetic field, and is experiencing a total...

Here on Earth there are three major geodynamos that generate the magnetic field. My question is about how they interact. My guess that while the axis of rotation of each field is different, the fields they generate tend to align. My further guess is that they do so only partially so that in...

Hello all!, first post here we go! I was hoping someone could answer a question for me because I can’t find the answer online. Or maybe point me to a magnetic field’s for dummies website.. I’ve been playing with a neodymium magnet shaped like a coin for a few days (yes easily occupied) and...

I want to perform an experiment to show that magnetic fields can control plasma. (Can even be a slight repulsion) Please Suggest one. I have no idea where I can obtain plasma - I have access to candle flame (though it's not a proper plasma) & fluorescent lights. I have a permanent magnet (not a...

The task is to find the magnetic field between the 2 long cylinders, which extend to infinity. Integration is involved to find the total current passing through the Amperian Loop shown below. What I do not understand is why only sides 1 and 3 contribute to that B ds part of Ampere's Law. Isn't...

What changes occur in electron, whenit through in a electric field

I thought it might be the case that the "2m away" wasn't applicable as the electric field doesn't change if the point away is less than the length of the plate, so I thought I should use the equation listed. All examples I can find talk about two charged plates, or the effect on cylinders...

I'm trying to the following exercise: I've proven the first part and now I'm trying to do the same thing for fermions. The formulas for the mode expansions are: What I did was the following: $$\begin{align*} \sum_s \int d\tilde{q} \left(a_s(q) u(q,s) e^{-iq \cdot x}+ b_s^\dagger(q) v(q,s)...

When the same author(s) write two books on the same topic, with one book being more elementary and less advanced than the other, then this more elementary book is called "baby". A well known example is baby Rudin for mathematical analysis. Another example is baby Reif for statistical physics...

Regarding this paper: https://iopscience.iop.org/article/10.3847/1538-4357/abbb96 In the opening sentence of the Abstract the following is stated: "The strong equivalence principle (SEP) distinguishes general relativity (GR) from other viable theories of gravity. The SEP demands that the...

I was trying to show that the field transformation equations do hold when considering electric and magnetic fields as 4-vectors. To start off, I obtained the temporal and spatial components of ##E^{\alpha}## and ##B^{\alpha}##. The expressions are obtained from the following equations...

1. When two parallel wires carry current in the same direction, they exert equal and opposite attractive forces on each other. 2. ε=lvBsinθ ε=0.02*5*0.1*sin30 ε=0.005 V 3. Well, a conductor moving through a magnetic field has the potential to induce an emf, but this movement must be in such a...

My attempt at a solution: Is my logic accurate/correct, and is my answer correct? I consider the forces acting to be: Restoring forces in springs parallel, and Force of the current-carrying conductor in the Magnetic field. I imagine a vertical displacement of y upwards ( direction determined...

Are you saying there are circumstances in which the work done in a magnetic field depends on the path taken?

a) is pretty clear and got correct but b) I'm struggling with. For b) I guess one could take the derivative of I and specify the moment t when you can plug that into Faraday's law. Or could this be solved somehow with inductance?

So, basically I can follow the math deriving E/B = c from Maxwell. And I can calculate B and H from I: H = I/2*pi*r and B=uH. Easy. So, for example I take a 2000 A, 50 Hz, current and a distance of 2 meter from that current in a round conductor. H and B are set: H = 160 A/m and B = 0,2 mT...

Poynting's Theorem (https://en.wikipedia.org/wiki/Poynting's_theorem) says: The rate of energy transfer (per unit volume) from a region of space equals the rate of work done on a charge distribution plus the energy flux leaving that region. $$-\frac{\partial u}{\partial...

I started from: $$\frac{d}{dt}(m\gamma v_x)=qE\ \ \ \rightarrow \ \ \ m\gamma v_x - p_{0x}=qE(t-0)\ \ \ \rightarrow \ \ \ m\gamma v_x=qEt+p_{0x} $$$$\frac{d}{dt}(m\gamma v_y)=0\ \ \ \rightarrow \ \ \ m\gamma v_y -p_{0y}=0\ \ \ \rightarrow \ \ \ m\gamma v_y = p_{0y}$$$$\frac{d}{dt}(m\gamma...

Good evening, I'm trying to solve this exercise that apparently seems trivial, but I wouldn't want to make mistakes, just trivial. Proceeding with the first point I wonder if my approach can be correct in describing this situation. From the assumptions, the two fields are in this...

The faster the relative speed or the more intense the gravitational field, the slower time passes. Does it make sense to ask what both have in common that affects time? Or does the question possibly only make sense in the context of certain theories, for example the LQG, where space and time...

I am looking at antenna theory and just came upon scalar fields. I found an site giving an example of a scalar field as measuring the temperature in a pan on a stove with a small layer of water. The temperature away from the heat source will be cooler than near it but it doesn't have a...

If time for something approaching the speed of light will slow down and approach zero, then how is it that light itself can exhibit changes - the oscillation of the E and B fields? Is it because those fields are perpendicular to the direction of light travel? If so, then something other than...

So I know the acceleration is 0, so the net force is 0. QE=1.6E-3*9.9E3 k hat = 15.84 k hat (thats one force) qv x B = q(v i hat + v j hat) x (0.51 i hat + 0.10 j hat) =q(0.10 v k hat- 0.51 v k hat) =q(-0.41 v k hat) =-0.000656 v k hat Now solving for velocity, 0.000656v=15.84...