# Electrostatic charges Definition and 27 Discussions

Electrostatics is a branch of physics that studies electric charges at rest.
Since classical physics, it has been known that some materials, such as amber, attract lightweight particles after rubbing. The Greek word for amber, ήλεκτρον, or electron, was thus the source of the word 'electricity'. Electrostatic phenomena arise from the forces that electric charges exert on each other. Such forces are described by Coulomb's law.
Even though electrostatically induced forces seem to be rather weak, some electrostatic forces such as the one between an electron and a proton, that together make up a hydrogen atom, is about 36 orders of magnitude stronger than the gravitational force acting between them.
There are many examples of electrostatic phenomena, from those as simple as the attraction of the plastic wrap to one's hand after it is removed from a package to the apparently spontaneous explosion of grain silos, the damage of electronic components during manufacturing, and photocopier & laser printer operation. Electrostatics involves the buildup of charge on the surface of objects due to contact with other surfaces. Although charge exchange happens whenever any two surfaces contact and separate, the effects of charge exchange are usually only noticed when at least one of the surfaces has a high resistance to electrical flow. This is because the charges that transfer are trapped there for a time long enough for their effects to be observed. These charges then remain on the object until they either bleed off to ground or are quickly neutralized by a discharge: e.g., the familiar phenomenon of a static "shock" is caused by the neutralization of charge built up in the body from contact with insulated surfaces.

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1. ### I Where to find this uniqueness theorem of electrostatics?

There is a nice uniqueness theorem of electrostatics, which I have found only after googling hours, and deep inside some academic site, in the lecture notes of Dr Vadim Kaplunovsky: Notice that the important thing here is that only the NET charges on the conductors are specified, not their...
2. ### Electric field due to three point charges

I've calculated the intensity for every point charge which are EA = 6.741 x 10¹³ NC¯¹ EB = 4.494 x 10¹¹ NC¯¹ EC = 6.741 x 10¹³ NC¯¹ and im pretty sure about this far but im struggling to calculate the X-axis intensity and Y-axis intensity to find the entire approximate intensity with the...
3. ### B Problems I Have With Electrostatics and Pith Ball Experiments

As a preliminary note, most people flex about how dumb questions and then continue to school and scold curious minds. Instead of taking a demeaning approach I just ask for respectful insight to quench curiosity. I will 1) explain the experiment as I know it to be, 2) explain what I have been...
4. ### Self Study - Foundations of Electromagnetic Theory Problem 2-1 (two charged particles hanging on strings)

I'd like someone to check that this solution is right, and if not, give me the point of failure and not the answer. Thanks!
5. ### Comparing energy lost by the battery & energy gained by the capacitor.

Imagine the two terminal of a *parallel-plate capacitor* are connected to the two terminal of a battery with electric potential difference #V#. If the capacitance of the capacitor is #C#, and the area of each plate is $A$. In this process would the energy lost by the battery and the stored...
6. ### B Electrostatic charge build up in environmental electron microscopy

Hello, If I understand it correctly, the samples are grounded inside a scanning electron microscope (SEM) to avoid charge build up through the electron beam. Also the non-conductive are coated with a conductive layer, so they can be grounded as well. However, I do not know how the charge build...
7. ### Can positive charge move between charged bodies like electrons do?

Suppose , there is a body B1(-vely charged) and body B2(+vely charged). When both are on contact, electrons move from B1 to B2 as B2 is having electron deficit. But is reverse also possible that protons move from B2 to B1 as B1 is having proton deficit.
8. ### Why the work done is negative when bringing 2 opposite charges together?

we know that if the applied force is in the direction of the displacement then work done is positive.But in case of bringing 2 opposite charges from infinite to a certain distance,the work done is negative even the force and the displacement of the charge is in the same direction. From...
9. ### Calculate the magnitude and direction of the torque

Homework Statement [/B] a) (a) Assuming the HCl molecule consists of point-like ions (H+ and Cl) separated by 1.0 * 10^-10m, find the dipole moment of the molecule. b) Calculate the magnitude and direction of the torque exerted on this dipole if the molecule is subjected to an external electric...
10. ### Point Charges on a Polygon with another Charge in the Middle

Homework Statement Suppose we have a regular n-gon with identical charges at each vertex. What force would a charge ##Q## at the centre feel? What would the force on the charge ##Q## be if one of the charges at the vertices were removed? [/B] Homework Equations Principle of Superposition...
11. ### Non-uniformly charged disc

Homework Statement I have a disc with radius R. One half has the charge density of +2σ and the other half has −σ. The task is to find the total charge of the disc. Homework Equations dQ=ρ2πr^2 I would use this equation if the charge density was uniform The Attempt at a Solution My first idea...
12. ### Problem in electrostatics: E-field near 2 point charges

Homework Statement Refer the image. Homework Equations kq1q2/r^2 = F Potential energy = kq1q1/r The Attempt at a Solution Obviously since both charges are unequal in magnitude option a is incorrect. Calculating field at large distance r, E = kq1/r^2 - kq2/r^2 = kq2/r^2 Also potential energy...
13. ### Electrostatic energy after a metal piece is inserted between 2 capacitor plates

Homework Statement fig 1 : Area of each plate is S, separated by 2d, charge Q in the capacitors fig 2 : uncharged conductors of area S, thickness d, inserted parallel between plates What is the ratio of electrostatic energy in fig 2 to electrostatic energy in fig 1? Homework Equations Q =...
14. ### Calculate the total force on Q1

Homework Statement Q1<------>Q2<------>Q3 In the above figure, the distance between Q1 and Q2 is equal to the distance between Q2 and Q3. That distance is R=1.5 m. Q1= 2.24x10-6 C, Q2=+Q1 and Q3=-Q1. Calculate the total force on Q1. Give your answer with a positive number for a force...
15. ### Electrostatics: Finding force experienced by charge

1. Find the magnitude and direction of the force experienced by the charge of 3microcoulombs. Homework Equations After subtending forces of both the particles on the third one, we need to find the aggregate magnitude of the charge experienced by it. The Attempt at a Solution I was able to...
16. ### How do I find the points where the electric field is zero?

Homework Statement Two pairs of charges are shown in Figure 1. Homework Equations The Attempt at a Solution I originally thought that the electric field past point 7 (i.e. points 8,9, 10) was the solution. However, this is wrong. I then considered point 1, yet that was wrong too. I even...
17. ### Electrostatics: Charging a sphere by induction

Homework Statement this is a theoretical question.please consider the situation as follows: we are charging a metallic sphere using induction phenomenon with the help of a postively charged metallic rod and while on grounding the electrons flow from the ground to the sphere rather than sphere...
18. ### Consider the configuration consisting a +q charge...

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...
19. ### B Why are two cellophane tapes attracted when ripped apart?

Hello, I put two strips of cellophane tape adjacent to each other adhered onto a table. When I pull them both apart, they repel each other, both insulators ripped electrons from the wood. When I stack two strips of tape on top of each other on a table, rip the combined bundle off the table...
20. ### Doubt from capacitors

can a charged capacitor mathematically be represented as uncharged capacitor connected in series with battery of opposing emf ?
21. ### Gauss' Law question

Homework Statement Consider two balls of equal radii and masses but opposite charges, distributed uniformly over their volumes. Initially, the balls are at rest and far away from one another. Due to the Coulomb attraction, the balls start moving towards each other. The balls can be treated as...
22. ### Net Electrostatic Force

1. The problem statement: In the figure four particles form a square with edge length a = 2.44 × 10-2 m. The charges are q1 = q4 = 1.06 × 10-15 C and q2 = q3 = q. What is q if the net electrostatic force on particle 1 is zero? All variables and given/known data: The given variable are in the...
23. ### Work done in electrostatics

Homework Statement A metallic sphere is placed inside a hollow spherical shell. The potential on the inner and outer spheres is 10 V and 5 V respectively. What is the potential at the center?(The spheres are concentric.) Homework Equations $$V =\frac{kq}{r}$$ The Attempt at a Solution The...
24. ### Problem with Net Coulombic Force

Homework Statement Consider an ## n ##-dimensional solid sphere of radius ##R##, with uniform charge-density and a total charge ##Q##. A charged particle ##q## is kept at a distance of ##r## from the center. For ##r<R##, what is the Net Coulombic Force experienced by the particle? If it is in...
25. ### Electrostatic Force Between Proton and Neutron?

After calculating the force upon an electron and a force upon a proton in the atom of hydrogen, my result was a force of ≈8.2x10-8 Newtons acting upon the electron and proton each. If found this by using the formula Fe = (ke q1q2)/r2 Taking this number, I then applied it in the formula F = ma...
26. ### + charged sphere and - charged sphere touch and seperate

Homework Statement A small metal sphere X is charged by losing 500 electrons. An identical metal sphere Y is charged by gaining 1000 electrons. The two spheres are first put in contact with each other and then separated. If -e is the charge on an electron, what is the charge on each sphere...
27. ### Differences in Repelling Charges

Simply, is there a difference between a positive charge repelling a positive charge and a negative charge repelling a negative charge. More of what I am asking, is there any special properties that one has over the other, and vice versa.