# Search results

1. ### Lorentz Force replaces 2 laws of Maxwell?

This. I'm pretty sure for the original integral form of Faraday's Law, its not about the magnetic field strength varying with time, but rather the magnetic FLUX through the coil (varying with time). And that shouldn't be a problem in calculation using only the Lorentz Force Law. So in other...
2. ### Lorentz Force replaces 2 laws of Maxwell?

Hey guys, I think we're missing the main question here, which is to put it rather crudely, can Faraday's Law of Induction be derived from the Lorentz Force Law(or maybe the other way around)? The short answer is probably no, but look at it this way. First of all, the original integral form...
3. ### Lorentz Force replaces 2 laws of Maxwell?

Are you sure? I've always thought that the Lorentz Force Law was needed in addition to Maxwell's Equations and cannot be derived from them. Maxwell's equations tell you what the fields are (if you solve them for every point in space and time), and the Lorentz Force Law tells you how the fields...
4. ### Lorentz Force replaces 2 laws of Maxwell?

Erm... I'm pretty sure the thread starter isn't talking about Ampere's Force Law and Faraday's Force Law(personally, I've never heard of a Faraday's Force Law), but IS talking about the ones in Maxwell's set of equations. What his question is, if I were to attempt to reiterate, is that the...
5. ### Schools National University of Singapore - Will going there limit my options?

I did check out the course information and stuff on their website, but I didn't attend the open house, if that is what you mean. I did consider it as an option.
6. ### Maxwell's equations VS. Lorentz & Coulomb force equations

Thats right, Biot-Savart and Coulomb's law are good approximations for the E-fields of slow moving charges, obviously the faster the charges are moving, the less accurate they become. I don't get what you mean. Your first statement contradicts your second. Y.) and Z.) are solutions from...
7. ### Maxwell's equations VS. Lorentz & Coulomb force equations

X.) Yes. Though I should say its not that it SHOULD be replaced, it just can be replaced. We normally use Vector Identities to simplify things, and not substitute directly. For example, we can take the curl on both sides of 3, then sub in the curl(B) from 4. Y.) No. Z.) No. Q.) Yes...
8. ### Maxwell's equations VS. Lorentz & Coulomb force equations

1) Already gave that to you. Check the previous post. 2) I have no idea what you're saying. Classical Electrodynamics is the basis for which the Lorentz transforms were developed the first time. 3) When we solved for E, we wanted to find it in terms of the velocity and acceleration of the...
9. ### Maxwell's equations VS. Lorentz & Coulomb force equations

No. You solve Maxwell's equations to obtain an expression for the E and B. These were taken from the Wikipedia link that you obviously didn't read(and have been posted twice in the thread). I think you might want to know what the the symbols mean(again from Wikipedia): is the...
10. ### How do magnetic fields do no work?

Wait so is the answer: 1. Magnetic fields never do work. or 2. Magnetic fields do no work by themselves? I'm guessing the answer is 2, because lets say if I have a square coil of wire, and I rotate it in a constant B-field, the magnitude of the velocity of a charge in the coil will simply...
11. ### Simple Harmonic Motion w/ postion function

g) You are right to say that the KE is at a maximum when the velocity is at a maximum(in magnitude). Hence the angle in the cosine function of v(t) must be an integer multiple of pi. Which leads to t = 1.5(I don't know how you got t = 4?), or if you know your trig, you can simply conclude that...
12. ### Schools National University of Singapore - Will going there limit my options?

I see. As of now I have little interest in applied Physics as well, but that scholarship looked interesting since there was no bond and all. And yeah I am also more inclined towards the theoretical aspects of Physics as well. Either way thanks for you help and I will post again if I have more...
13. ### Hypothetical kinetics questions, just for fun

In a regular pendulum motion(the A path), the tension in the web would depend on the angle of elevation at that point in time. So you end up with T = W sin(a), where T is the tension and W is the weight of spiderman, a is angle of elevation. Now to travel in a straight path(B path), the total...
14. ### Schools National University of Singapore - Will going there limit my options?

Thanks you for your reply! Yes, I did realize, upon reading some university texts in my free time, the amount of mathematics in Physics is a lot more at the university level than at the A-level. That is a good thing at any rate as A-level physics(or science for that matter) was rather...
15. ### Schools National University of Singapore - Will going there limit my options?

Hello all. As a Singaporean who has just received his 'A' level results, I am currently wondering if the NUS Physics faculty has a good reputation globally. An online search seemed to show that it stood around the mid region overall (ranked 30 or so). The question that bothers me is whether or...
16. ### One of the most fundamental questions in electric currents (basic but very important)

There is a uniform E-field within the wires if its a DC source, so the electrons are constantly being accelerated(pushed).
17. ### What type of energy is transfered in a circuit?

Oh I see. Its because fundamentally there are only 4 forces, so am I right to say that when we talk of 'collisions' taking place, they are simply some electromagnetic forces between electrons and the particles in the material which affect the electrons motion? Sorry for reiterating what you...
18. ### The upward Force

Speaking of pressure, is there a way to show a fluid exerts equal pressure in all directions mathematically? Like for ideal gases we can use the assumption that collisions with the walls of the container are perfectly elastic to show that pV =1/3Nm<v^2> where <v^2> is the mean square speed of...
19. ### What type of energy is transfered in a circuit?

Okay I think this sort of clears it up. Thanks a lot. So to sum it up, the collisions in the Drude model are simply useful in portraying power output due to resistance, but for everyday uses like my computer for instance, it depends on how the individual circuitry is designed to extract power...
20. ### What type of energy is transfered in a circuit?

Yeah I sort of meant something like that. Not exactly colliding and stuff. More like an electron moving against another force while still under the force of the E-field. Like that the block on the table, if there was no load attached to it, it would have gained more KE, but work has to be done...
21. ### What type of energy is transfered in a circuit?

I am confused by the AC part. Isn't an AC produced by a coil of wire placed within a uniform magnetic field and rotated to change the magnetic flux through it, inducing a potential? Or is this a simplified explanation of how an AC generator works that doesn't talk about EM waves and such...

I'm not exactly sure on this since I've only read a very layman explanation for it. Basically, from what I read, using your light bulb example, the charges near the bulb 'feel' the acceleration due to the emf from the power source almost immediately as the E-field changes due to the source...
23. ### What type of energy is transfered in a circuit?

So what happens to the KE that the electrons are supposed to gain? The E-field produced by the battery exerts a force on the electrons, causing them to accelerate and hence gain KE. Even in an AC circuit, while the electrons have no net displacement, the direction of the force due to the AC...

The electrons themselves move at a low average drift velocity, but the current in the wire moves at close to the speed of light.
25. ### What type of energy is transfered in a circuit?

I'm not quite sure how this works. Isn't the reason that electrons possess low average KE because they've transferred most of their KE to other forms in the components? For example, in the absence of components(hence no or negligible resistance), an electron traveling through a circuit with a...
26. ### Electric fields between point charges

Nope. Its only constant between two (infinitely large) parallel charged plates because you're summing the electric field due to all point charges on the plate. The many charges spread out on the plates all contribute to the electric field at some point between the plates. Doing the summation...
27. ### Describing chemical potential in Galvanic cell using Coulomb Force/Electric Potential

Placing a block of metal in a solution of its ions causes it to go into some kind of dynamic equilibrium such that the metal ions form from atoms and atoms from ions at the same rate. In the first place why does this phenomena occur? Is it something that can be described using Physics...
28. ### Quantum Tunneling: Observed properties of the particle within the barrier.

Hi. Firstly, can a particle every be found within the potential barrier? I've used the search function to look for an answer for this question, but I didn't really get anything conclusive. However, from what I gather, since there is a probability associated with it being 'found'(meaning it...
29. ### The distance from the Earth at a given time t for a body moving toward the Earth.

Suppose an object is moving toward the Earth(with a direction perpendicular to the Earth's surface) at an initial speed v0, starting from a distance r0. The object also experiences gravitational acceleration. Is it possible to obtain an expression of r as a function of t? In other words, whats...
30. ### Complex numbers (2)

Well... Using De Moivre's theorem, there are actually 3 solutions for that equation. Because 2 + 2i can be expressed as 2\sqrt{2}ei(\pi/4) = 2\sqrt{2}ei(\pi/4+2k\pi). so Z3 = 2\sqrt{2}ei(\pi/4+2k\pi) => Z = (2\sqrt{2}ei(\pi/4+2k\pi))(1/3) for any 3 consecutive values of k.