Outside Definition and 469 Threads

My textbook says "the net flux is zero through a closed surface that does not contain any net charge," and justifies it by saying that everything flowing in has an equal thing flowing out. This makes ABSOLUTELY NO sense to me.

All that is visible to the human eye is that which can be seen at the furthest limits of the Cosmos, which began with the Big Bang. So then, what could exist from that point on? What space or material is the expanding Universe encroaching into, and either pushing it away, or transforming it into...

In Gaus's law when the integral is set up, we don't account for the charge outside the closed area. Why is this? How does this law work when the charges outside are not accounted for and only the charges enclosed is in the equation? I need an explanation why Gaus's law still works for...

A point charge outside a hollow conducting sphere will produce no field in the hollow interior: the metal shields the interior. But a point charge inside the hollow interior will produce a field outside: the same metal ceases to act as a shield. Why is this? (In particular, aren’t “inside” and...

I am working on a problem of electrostatics, and I am having troubles in trying to figure out one part of it. 1. Homework Statement It consists of an inner solid cylinder of radius ##a## with a voltage ##V_A##, and an outer coaxial cylindrical shell of inner radius ##b## and outer radius ##c##...

Homework Statement A cup of boiling water is placed outside at 1:00 PM. One minute later the temperature of the water is 152 degrees Fahrenheit. After another minute its temperature is 112 degrees Fahrenheit. Find the outside temperature. Homework Equations None. The Attempt at a Solution...

Well, here in Toronto, ON, Canada, it is currently -9 deg Celsius with a windchill of -18 deg Celsius (for Americans, that is 16 deg Fahrenheit with a windchill of -0.4 deg Fahrenheit). Tomorrow Toronto is expecting a high of -11 deg Celsius (12 deg Fahrenheit) with a windchill of -22 deg...

There are a lot of florescent proteins in the visible range, but why haven't we fount any above or below that range? I think a protein that emits radio waves could be very helpful both biologically and scientifically. Are we not looking for such proteins, or do they not exist?

Looking at different graduate programs to apply to for physics focusing on biological physics. Very different research going on from school to school in the field so most of the criteria I'm basing where I apply is what kind of research is listed. My understanding of the process at your given...

I read that viruses outside the host remain infectious only for a short time; hours or days. What happens to them? How are they damaged? A second related question. All living organisms require an external source of energy to survive (correct?) The words live and die are hard to apply to...

The potential on the side and the bottom of the cylinder is zero, while the top has a potential V_0. We want to find the potential outside the cylinder. Can I use the same boundary conditions as for case of inside cylinder potential? What is different?

I am a senior undergraduate physics major but I am not sure I want to go to graduate school for physics. I do not actually enjoy physics. I find it do-able but I started realizing junior year that I definitely don't love it. I have had a subscription to physics today for three years and never...

Homework Statement What is the electric field at a point .12m outside the surface of an isolated plastic sphere .23m in diameter that produces an electric field of 1350 N/C just outside the surface of the sphere? Homework Equations E = kQ/(r^2) The Attempt at a Solution First I...

Case 1. You have a sphere with Radius R and middle point X with the charge Q. The charge is equally distributed over the sphere. for E(X,r) = 0 for r_1 < R, E inside the sphere is 0. If r_2 > R then E ≠ 0 ; but let's say E(X,r_2) := w If you put all the charge of the sphere into X then...

Hey guys! Let me throw in who I am before I introduce my question. I finished my year of graduate school last May, figured out an advisor and a field (something related with Brownian motion on manifolds), and I'm overall happy with it all. No plans of dropping out, I enjoy the company of my...

Hello , please help me out , I can find the E field of a sphere on google and read that there is no field on the inside of the sphere , but what is the e field of a torus ? Not on the inside but on the outside surfaces also in the inner loop or the middle ?

What is difference between iron that we use in food...and iron metal

Finding the magnetic field for a straight wire using the right hand rule shows that the field is around the wire. Applying this same concept for a toroid, the magnetic field inside is central to the loop of wires so that makes sense. However, isn't there also a magnetic field outside in a...

http://arxiv.org/abs/1407.0989 White hole anyone?..^^ "...intense gravity creates a horizon, but it is not an event horizon. It is locally like an horizon, but not globally. So, matter is trapped for a while, but not forever; it is called sometimes a “trapping” horizon."-CR

Homework Statement Two non conductive shells surround each other, with radius r1, r2 and charges q1, q2 respectively. Find electric fields for E(r < r1), E(r1 < r < r2), E(r > r2) r1 is the inner shell, r2 is the outer shell (r1 < r2) Homework Equations I'm using gauss' law flux = E * A =...

Hi, I'm having a strangely hard time imagining how the distribution of particles would look around a constant point source in some scenarios. I came up wiith something that sounds reasonable to me, but would like a logic check. The easy one for me to grasp is distribution when the source...

Is there a way to determine the temperature outside without using a thermometer? Any formulas I could use?

Homework Statement A dipole is placed next to a sphere (see image), at a large distance what is E proportional to? 3. The Attempt at a Solution or lack thereof I'm having trouble figuring out what's happening in any variations of these. How does the dipole affect the sphere's charge...

I am an indian student finishing my undergrad this year and planing to apply for masters or Phd. Are there any notable and well known physics schools other than the ones US that i can consider applying to ? Like what are the options available other than US schools for masters program...

What i mean is: are there currently Higgs Bosons in the universe or the only place where they exist now is if man (or some other technological being) recreates special conditions like in a particle accelerator? Another related question of mine is: some particles "receive" their mass from the...

I'm really stumped here as usual. Here is what I've managed to figure out. I'm given two equations. r=2 r=4cos(theta)I converted them both to rectangular coordinates to get an idea of what the graph would look like. I need to find either the area in red or the area in green. (In this case...

Homework Statement A solenoid has a radius of 1.85 cm and 1110 turns per meter. Over a certain time interval the current varies with time according to the expression I = 2.50t, where I is in amperes and t is in seconds. Calculate the electric field 5.47 cm from the axis of the solenoid...

Homework Statement A solenoid has a radius of 2.10 cm and 1180 turns per meter. Over a certain time interval the current varies with time according to the expression I = 1.30t, where I is in amperes and t is in seconds. Calculate the electric field 4.65 cm from the axis of the solenoid...

A colleague and I want to model how a slab of PCM (wax) solidifies as it cools off. What I have noticed in my experiments is that temperature sensors on the top and bottom of the slab say it should be solid, as they read well below the melting point. But when I peek at the sample, the center...

My book says it is zero, but I don't know where to start , why is it zero ? I have to take an exam in few hours :cry: so a simple explanation would be appreciated ( I'm not studying pure physics:smile: Here are the electric fields of the three regions . Thanks in advance :smile:

Yesterday, I read about Hawking's new proposal regarding the firewall paradox. A more general thought about standard black holes occurred to me. Black holes including stellar black holes are of course always presented as if the event horizon is an invisible barrier, which the unfortunate...

For question 4b in the problem sheet attached below, is my working correct for B outside and inside the coaxial cable? Ans: Outside coaxial:∫B.dl = μI (the integral is between 0 and 2∏r) => B = (μI)/(2∏r) Inside the coaxial: \int_{2\pi a}^{2\pi r} B.dI = μI.\frac{a^2}{\pi...

Okay, this might be a stupid question, but I have a sheet with all the formulas to find all kinds of anything you'd need to find about a gear. However I am confused by when it says outside diameter. Is outside diameter the same as circumference? How do I find outside diameter using either the...

Hello Friends, in my textbook it is written that in electrostatics,electric field(E) due to a conductor at an external point very near to it is given by σ/ε.where 'σ' is the local surface charge density and 'ε' is epsilon.they have derived it by using a symmetrical conductor which have...

Homework Statement Find the potential outside a charged metal sphere (charge Q, radius R) placed in an otherwise uniform electric field E0. Explain clearly where you are setting the zero of potential. Homework Equations The Attempt at a Solution My only problem here is that I...

Hello physics forums, Say you had a hollow steel sphere of thickness 1 mm and diameter of 1 meter (from outside to outside)? Inside the sphere is gas at 1 atm pressure. Outside is 1 atm of pressure. How much gas would I have to remove from the inside until the sphere collapsed from...

I am trying to understand why the magnetic field outside a solenoid of very long length can be assumed to be near zero. I gather that the field inside the solenoid will be very dense and therefore strong, and that the field lines that loop back round outside the solenoid can spread out. Is...

In various other threads we have been kicking around various equations for a spherical shell and discussing the implications. In this thread I would like to present what (I think) I have worked out about how the shell metric relates to the vacuum metric inside and outside the shell. I hope to...

What happened about inside forces? For example If we are "out" of a chair,we can lift that,but If we are sitting we can not lift that. I know that we can not "fly",so that is a reason,But I need physics reason. Thanks!

Okay, so I did a lab where we had a 2 pulley system that involved a string and three masses. The string is set up so it is in the shape of an m when put on the pulleys. The known mass is put on the middle string (m3) hanging down and the two outside masses (m1) and (m2) are unknown and are not...

I just registered and am not entirely sure this is the right section of the forum to ask, but regardless... My understanding of gravity is that it is a wavelike distortion in spacetime which travels not instantaneously but at the speed of light, and may also be describable in terms of a stream...

Homework Statement A solid non-conducting sphere of radius R = 1.12m. The sphere posses a total charge Qtot spread uniformally throughout its volume. a) derive equations for electric field for 1) 0<r<R 2) r>R result in terms of r R and Q b) Derive an equation that gives...

Homework Statement A circular metal plate of radius 0.2 m has 1010 excess electrons uniformly distributed over its surfaces. What is the magnitude and direction of the field just outside the plate near its center? Homework Equations E = kQ/r2 The Attempt at a Solution Starting with E =...

Homework Statement A long, straight wire of radius a has current density J = J0e−β(α−ρ)uz where β is a constant and ρ < α. Determine B inside and outside the wire.Homework Equations J=I/((pi)a^2) B=(μIρ)/(2(pi)(a)^2) The Attempt at a Solution Here is what I did B=(μρ/2)J0e^(-β(alpha-ρ))

Homework Statement Consider a hollow cylinder of radius 10 m., length 50 m., and charge 6 C., and a rod with radius 4 m., length 50 m., and charge -4 C. The rod is uniformly placed inside the center of the hollow cylinder. What is the electric field at radius = 15 m.?Homework Equations...

This is not a joke. Is it by all accounts impossible to do this, supposing that an artificial heart with artificial blood transport systems (that provide oxygen and all needed nutrients) were used to keep the cells from dying. Also, assuming the brain was yours, what would it feel like to...

Hi, I recall some years ago seeing a composite picture of what our galaxy would look like from outside the galaxy, for example from Andromeda but was not able to find one or even how to search for it on the web. I was wondering if anyone here is familiar with it and perhaps even if we've...

I am in my last year of high school. I do not know if I will become a mathematician or physicist. Right now, I enjoy physics more but I will double major in math and physics anyway. I know that research experience is important in undergraduate physics. However, how important is undergraduate...

Homework Statement Begin from the expression of the electric field outside an infinite sheet of uniform surface charge density, E=\frac{σ}{2\epsilon}. Derive the electric field just outside an ideal conductor: E=\frac{σ}{\epsilon}. Do NOT use Gauss's law. Homework Equations Not sure...

Hello, Am not studying biology am engineer but iam just wondering if it is possible to make a muscle contract through external voltage maybe through some electrodes connected to some area on the skin. Regards Hisham