Charge Definition and 1000 Threads

Hi. If an electrically neutral, conducting rod is brought close to a (say negatively) charged object with one end, charges will separate due to electrostatic induction roughly as follows: Let's now connect the rod to the (far-away) ground with a long cable. Does it make a difference whether...

Homework Statement Four charges, q1 = +145 µC, q2 = +55 µC, q3 = −150 µC, and q4 = +27 µC, are fixed at the corners of a 4 m by 5 m rectangle, as illustrated in the figure below. What are the magnitude (in N) and the direction (in degrees counterclockwise from the +x-axis) of the net force...

Homework Statement The electric dipole moment for the water molecule equals $$ p = 6.13 × 10−30 C · m $$ Suppose that in the glass of water all molecular dipoles could be made to point down. Calculate the resulting surface charge density at the upper water surfaceHomework Equations [/B] ## P...

Homework Statement Homework Equations .Q = CVab The Attempt at a Solution I am having a hard time understanding when to put the capacitance in the denominator. I get that Voltage = Charge/Capacitance, but for the equation circled in red "q1/c + q2/c = q3c" ... I don't get why each of...

Homework Statement Assume you have C1, C2, C3 capacitors and each one of them have a specific charge. Now imagine you connect them to one circuit (Just as in the picture below). Determine the charge on each capacitor after the movement of charges stop Homework Equations Kirchhoff's law The...

Homework Statement A line of charge of uniform density ρl occupies a semicircle of radius b as shown in Fig. P4.10. Use the material presented in Example 4-4 to determine the electric field at the origin. Homework Equations dE = kdQ/r^2 The Attempt at a Solution I'm trying to understand the...

Hello, I am building a power bank myself and want to set put detector that determines the voltage level and indicates it in LED (4 LED are planned to be used). I know how to make it with transistors and op amp. But I was wandering if there is any IC chip that does it? Thank you, Akmalidin Alimov

Hi. If a plate capacitor is charged with some charge ##Q##, then there's a voltage ##U=Q/C## between the plates. The electric field between the plates is ##E=U/d##. Voltage is path independent, if I connect the plates with a cable of length ##l\gg d## the voltage across the cable is the same...

Homework Statement For a model of a proton's charge distribution, : [/B] I have to find the constant of normalisation for rho. Homework EquationsThe Attempt at a Solution [/B] I wrote p(r)=p_0 * (e^-r/R)/r I then wrote it as p_0^2 * integral from -infinity to +infinity of (e^-(r/)^2)/r^2 =...

Homework Statement Hi everybody! I'm preparing for an exam of electromagnetism, and I am struggling with the last question of this problem (hopefully the two first ones are correctly solved): Given potential: ##\phi(\vec{r}) = k \frac{q}{r} e^{-r/R}## with ##r=\sqrt{x^2 + y^2 + z^2}## and ##R...

Homework Statement What is the magnitude E of the electric field at point P? Throughout this part, express your answers in terms of the constant k, defined by k = 1/(4πE0) To solve this question, I am trying to walk through the hint process. Question 1: Find the magnitude dE of the electric...

Hi. I understand a lightning rod reroutes the current of a lightning around an object, e.g. building. The lightning will preferably strike the rod because the electric field is strong at sharp points and the air is more likely to be ionized there. But does it also avoid lightning by giving off...

Homework Statement In the circuit shown in the figure, C1 = 1.0 µF, C2 = 1.9 µF, C3 = 2.8 µF, and a voltage Vab = 30 V is applied across points a and b. After C1 is fully charged the switch is thrown to the right. What is the final charge and potential difference on each capacitor? Homework...

Homework Statement What potential difference is needed to give a helium nucleus (Q = 3.2 × 10-19 C) 50 keV of kinetic energy? Homework Equations V=U/Q 3.2 × 10-19 C = 2e The Attempt at a Solution I was quite sure I had the right answer but it keeps saying I'm wrong? V = (50*10^3 eV) / 2e =...

Homework Statement An electric dipole consists of +/- Q = 330nC separated by a distance of 1200nm. The dipole is initially oriented in the -i direction (along the negative x axis). The dipole is in a uniform external electric field of E=2500j N/C Determine the following: a) The magnitude of...

What is electrical charge? is it a measure of the abundance of electrons within a system? Current is defined as the amount of charge flowing between any two points in a system over a given period of time, correct? but what is elctrical charge if possible to define it better/further. I am...

Homework Statement A point charge q is located a distance d away from the centre of a grounded conducting sphere of radius R<d. I need to find the charge density on the sphere and the total induced charge on the sphere. This is very similar to example 2 here...

I thought that insulators cannot be charged in the inside or the outside, so how can they have any charge density inside? I know that electric fields pass through a insulator, so is that why they can have charge density? I am currently reading about electric flux.

Homework Statement Prove that the Noether charge ##Q=\frac{i}{2}\int\ d^{3}x\ (\phi^{*}\pi^{*}-\phi\pi)## for a complex scalar field (governed by the Klein-Gordon action) is a constant in time. Homework Equations ##\pi=\dot{\phi}^{*}## The Attempt at a Solution...

At this point I was given rho, sigma and landa to hold value of these three different kinds of density ρ = Charge/Volume -------------- Volume Density σ = Charge/Area ----------------- Area Density λ = Charge/Length ---------------- Length Density How do I know which type of density to use over...

and two -q charges aligned along the x-axis as follows... -q__________q__________-q <--- the space between them being d a) Suppose the +q charge is displaced perpendicularly by a small vertical distance dy. What is the total force F acting on it? Taylor expand your answer to leading order in...

Homework Statement Consider the charge distribution of a uniformly charged ring of radius ##R## and charge ##Q## at a distance ##d## above the origin and a uniformly charged ring of radius ##R## and charge ##-Q## at a distance ##d## below the origin. (a) Calculate the dipole moment of this...

Note from mentor: this thread was originally posted in a non-homework forum, therefore it lacks the homework template. I was wondering if the electric charge density ##\rho({\bf{r}})## of a point charge ##q## at position ##{\bf{r}}_{0}## is given by...

Homework Statement A small object with mass m, charge q, and initial speed v0 = 6.00×10^3 m/s is projected into a uniform electric field between two parallel metal plates of length 26.0 cm(Figure 1) . The electric field between the plates is directed downward and has magnitude E = 600 N/C ...

Hello! I am bit confused about kirchhoffs law with capacitors. So if I have a battery and resistance, I obtain V-RI=0. But from what I read, if I have a capacitor and resistance (so discharging capacitor), the equation reads R(dq/dt) + q/c = 0, which is equivalent to RI + q/c =0. Why in this...

Homework Statement Homework Equations Work = - (integral of) (E dot dl) The Attempt at a Solution Hi, I know that the right answer is D zero, but I fail to understand why. I said that the answer was A as I have different charges, and I thought that depending on how I approach each...

Homework Statement Two particles 1 and 2, each carrying 6.0 nC of charge, are located along an x axis, one particle atx=−30 mm and the other at x = 30 mm. Where along the y-axis is a particle 3 carrying a charge of +2.0 nC if it experiences an electric force of 6.9 × 10^−5 N ȷ^? Homework...

Homework Statement I did a lab involving Van de Graaff generator. Basically, below the charged sphere, I put a neutral sphere on a scale and measure the difference in mass which then I can calculate the force acting on the neutral sphere. I repeated the experiment with different distance. What...

1) If I vary charge densities, but keep current density constant, do I get any sort of electromagnetic wave? 2) If the answer to question 1 is no, then if I vary charge densities, but keep current density constant, could I conceivably have a two isolated "open circuit" current elements of...

Hello Ads say a gyroboard with the battery 48V 4.4AH, and the motor 700 Wt will run for 2 hours at the speed of 20km/h ! But - simple physics - will not the motor drawing about 10-15 Amp exhaust the battery in just some 20 minutes !? Do ads lie ?

Sorry I couldn't finish the title. I ran out of space. Anyway, here's the question: A uniformly charged, infinitely long line of negative charge has a linear charge density of -λ and is located on the z axis. A small positively charged particle that has a mass m and a charge q is in circular...

Homework Statement Four uncharged metal plates of the same area are placed in vacuum and separated by equal distances. They are connected by conducting wires to two resistors, two open switches and a battery. The thickness of the plates is negligible, and their area is sufficiently large. S1 is...

Homework Statement When a -2C is moved from point A to B, the potential energy of the system increases by 10J. What is the voltage V(ab)? Homework Equations U=qV The Attempt at a Solution 10=(-2)V, I thought the voltage was -5V but the correct answer is +5V. Could someone explain why this is?

Homework Statement In a cubical volume, 1.05 m on a side, the electric field is given by the formula below, where E0 = 1.25 N/C and a = 1.05 m. = E0(1 + z/a) i + E0(z/a) j The cube has its sides parallel to the coordinate axes, see the figure. Determine the net charge within the cube...

Homework Statement Suppose the nonconducting sphere of Example 22-4 has a spherical cavity of radius r1 centered at the sphere's center (see the figure). Assuming the charge Q is distributed uniformly in the "shell" (between r = r1 and r = r0), determine the electric field as a function of r...

So why do Quarks have fractional non-discrete charge? Wouldn't it just be easier to just define ##\frac{1}{3}e## as +e and vice versa to preserve the discreetness of what we define as e?

is there any way to fully neutralize a charged metal plate ? connecting it to metal body of relatively huge capacitance will make its charge negligible but not zero? is there any other way?

The other day we were working on a problem which stated : Q charge is given to the positive plate of an isolated parallel plate capacitor of 10 μF. Calculate the potential difference betweeen the plates. Our teacher said that as the plate is isolated, Q charge will be divided between the two...

Homework Statement Two identical balls (B and C) with a mass of .5 g are suspended from two strings as shown above. The balls carry equal charges +10nC each and are separated by a distance of 4 cm. A. Draw the free-body diagram and show all forces applied to ball C. B. Find the tension force in...

Homework Statement A positive charge Q1 = 7.4 μC is located at a point X1 = -2 m, a negative charge Q2 = -9.7 μC is located at a point X2 = 3 m and a positive charge Q3 = 2.1 μC is located at a point X3 = 9 m. Draw free body diagrams for the electric force acting on Q1, Q2 and Q3. Find the...

Homework Statement A semi-circle of radius R has a charge Q uniformly distributed over its length, which provides a line charge density λ. Determine E at the origin. Homework EquationsThe Attempt at a Solution https://www.physicsforums.com/attachments/105239 I can tell by argument of...

Homework Statement Homework Equations There are no equations here, only theoretical knowledge The Attempt at a Solution Hi, My approach was this: I know that with the positive charge on the sphere being lowered into the cup I will have the inner area of the cup have a negative charge and...

Having read several introductory notes on Gauss's law, I have found it very frustrating that when the author comes to discussing the standard examples, in which one considers symmetric charge distributions, they do not explicitly discuss the symmetries of the situation, simply stating that, "by...

So the potential inside a conductor is constant. Does this mean that if there were a conductor, B, inside another conductor, A, the charges of A/B would redistribute such that the electric field inside would be zero (hence constant potential)? This seems logical but a bit too easy? Also, if it...

I've been looking through the internet and so fair I haven't found anything too clear on this. Some articles have said that plasma can be affected by magnetism and can be conductive, but my question is, will it become positively/negatively charged while current is flowing through it, and if it...

Homework Statement There's a uniform infinite line charge with the charge density λ. A point particle with charge q moves with a velocity v parellel to infinite line. What is force exerted on point particle? What is magnetic field seen in ths moving frame(particle frame)? Homework Equations...

You have two electrons held at a fixed distance X from each other. You measure the opposing force is Y. Now you bring the electrons closer to each other, and then let them go so they can fly apart. As the electrons move apart and reach distance X, will the opposing force still be Y, or will it...

The electric field inside an uncharged metal sphere is initially zero. If the sphere is the positively charged, the field at the center of the sphere will be...?

Hello, I have recently bought 4 cylindrical lithium ion batteries from hobby king to make a battery pack. To do this, I put all 4 of them in Parallel, so that the voltage would stay the same, but the capacity would increase. It says on Hobby king that they can charge at 5C, and since they are...

Homework Statement [/B] Two conducting spheres are far apart. The smaller sphere carries a total charge Q. The larger sphere has a radius that is twice that of the smaller and is neutral. After the two spheres are connected by a conducting wire, the charges on the smaller and larger spheres...