Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. There are two types of electric charge: positive and negative (commonly carried by protons and electrons respectively). Like charges repel each other and unlike charges attract each other. An object with an absence of net charge is referred to as neutral. Early knowledge of how charged substances interact is now called classical electrodynamics, and is still accurate for problems that do not require consideration of quantum effects.
Electric charge is a conserved property; the net charge of an isolated system, the amount of positive charge minus the amount of negative charge, cannot change. Electric charge is carried by subatomic particles. In ordinary matter, negative charge is carried by electrons, and positive charge is carried by the protons in the nuclei of atoms. If there are more electrons than protons in a piece of matter, it will have a negative charge, if there are fewer it will have a positive charge, and if there are equal numbers it will be neutral. Charge is quantized; it comes in integer multiples of individual small units called the elementary charge, e, about 1.602×10−19 coulombs, which is the smallest charge which can exist freely (particles called quarks have smaller charges, multiples of 1/3e, but they are only found in combination, and always combine to form particles with integer charge). The proton has a charge of +e, and the electron has a charge of −e.
Electric charges produce electric fields. A moving charge also produces a magnetic field. The interaction of electric charges with an electromagnetic field (combination of electric and magnetic fields) is the source of the electromagnetic (or Lorentz) force, which is one of the four fundamental forces in physics. The study of photon-mediated interactions among charged particles is called quantum electrodynamics.The SI derived unit of electric charge is the coulomb (C) named after French physicist Charles-Augustin de Coulomb. In electrical engineering it is also common to use the ampere-hour (Ah). In physics and chemistry it is common to use the elementary charge (e as a unit). Chemistry also uses the Faraday constant as the charge on a mole of electrons. The lowercase symbol q often denotes charge.
Homework Statement
Take two charges, one positive with charge q+, and another with charge q- are at a distance d away from each other. Under what conditions is there a point of equilibrium and, if it exists, where would it be located? Show mathematically. (Hint: use the quadratic equation...
Hi guys I am new here.
I was asked by my professor a problem:
a positron-electron pair is produced at the leftmost position of a 1D circular loop of radius R. e+ moves along the bottom hemisphere and e- moves along the upper one. They are confined in the circular loop and perform circular...
Homework Statement
The Problem is as follows :-
https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-snc6/224892_2277870043526_218311126_n.jpg
Three capacitors of 2 μF, 3μF, and 5μF are indulgently charged with batteries of emf’s 5V,20V and 10V respectively. After disconnected...
I am confused as to how Gauss's law can hold for moving charges. When discussing how to use Gauss's law to calculate the charge of a moving object, my textbook says:
"At the instant the moving charge passes the center of the sphere, the force on each test charge is measured, and the average...
I have a quick question about understanding the theory behind point charges and electrostatic potentials. I've not had any classes in electrodynamics, so I lack a comfortable foundation to help me think about these problems.
I need to determine the electrostatic potential a certain distance...
Homework Statement
I have a quick question about understanding the theory behind point charges and electrostatic potentials. I've not had any classes in electrodynamics, so I lack a comfortable foundation to help me think about these problems.
I need to determine the electrostatic...
[b]1. Five charges of 1.00 μC magnitude are placed in a row, each charge being 1.00 m distant from its neighboring charges. If all chargers are positive, what is the magnitude in N/C, of the electric field at the position of charge 4?
A) 0
B)2.13x10^-2
C)3.25x10^-3
D)3.25x10^3
E)2.13x10^4...
Homework Statement
The energy stored by any pair of positive charges is inversely proportional to the distance between them, and directly proportional to their charges. Three identical point charges start at the vertices of an equilateral triangle, and this configuration stores 15 Joules of...
Homework Statement
The 2.1mm diameter spheres in the figure are released from rest. What are their speeds vc and vd at the instant they collide?
Spheres:
C has 2nC of charge and a mass of 1g.
D has -1nC of charge and a mass of 2g.
The starting distance between the two spheres is 10mm...
Homework Statement
You have 3 charges, all +2.5 μC arranged on a field at positions (-3.0 cm, 0), (3.0 cm, 0), and (0, 3.0 cm). I have already calculated the stored electric potential energy to be 3.85 J. The question is: If the third charge (0, 3.0 cm) is released from rest, what is its change...
Homework Statement
A +15μC point charge Q1 is at a distance of 20mm from a +10μC charge Q2. Explain why there is a point along the line between the two charges at which the electric field strength is zero. After this, calculate the distance from this point to Q1 and Q2.
The Attempt at a...
In my chapter about electric fields in matter my book derives and expression for the potential due to the polarization of a dielectric material. For that you find that the polarization is equal to the potential of a collection of negative charges on the surface and positive charges inside the...
Imagine that an electron is traveling with velocity +v inside a uniform sphere of charge at potential +V.
In the rest frame of the electron the charged sphere has velocity -v.
Thus in the rest frame of the electron, inside the charged sphere, there is a vector potential A given by
A = -...
Imagine a cube with side lengths 'r', (like a dice) and we put point charges of charge Q at each corner of the cube.
Issues with 2 subsections of this problem...
First: What is the total electrostatic potential energy of the arrangement?
Second: Add a charge -CQ to the center of the cube for...
Upon reading about bound charges I stumbled on something I didn't quite understand. It is not a physical thing but purely a mathematical thing.
In the attached section my book wants to take the gradient:
∇'(1/r)
with respect to the source coordinates, r'. Now, can someone by inspection...
If I have a cube with a charge q at each corner, but the problem doesn't say anything about the cube being grounded. Can I assume that the total potential energy will be a linear combination of the individual six sides?
Homework Statement
Find the charge Q that should be placed at the centre of the square of side 8.50E+0 cm, at the corners of which four identical charges +q = 3 C are placed so that the whole system is in equilibrium.Homework Equations
F=(k*q1*q2) / r^2 The Attempt at a Solution
I know the...
Point charges q1 and q2 lie on the x-axis at points x = -a and x = +a, respectively. (a) How
must q1 and q2 be related for the net electrostatic force on point charge +Q, placed at x = +a=2,
to be zero? (b) Repeat (a) but with point charge +Q now placed at x = +3a=2.
Can someone help me...
Homework Statement
Charges q and -Q lie on the x-axis at x = 0 and x = d respectively. Charge -Q has a greater magnitude than q. In which region or regions on the x-axis is there a position where the electric field is zero?
A) x < 0
B) x < 0 and x > d
C) 0 < x < d and x > d
D) x > d
E)...
Homework Statement
Consider and electron being ejected from the surface of a heated filament at nearly zero speed. Through what potential difference must it be accelerated to achieve a speed of 8.4x10^6 m/s?
Homework Equations
I have found that the equation I should be using is 1/2mv^2=eΔV...
Homework Statement
Find the amount of charge required to double the radius of a bubble of radius r and surface tension T.Homework Equations
Increase in surface energy of bubble = T ΔA
The Attempt at a Solution
I've tried equating the increase in surface energy to the work done by the Coulomb...
I have a quick question about the retarded time when dealing with moving charges.
The retarded time is:
t' = t - \frac{r}{c}
where r is the distance between the point of observation and the position of the charge.
My question is very simple, is r a function of the normal time t , or...
Homework Statement
https://img.skitch.com/20120425-x1ekh2xqk9j61xqk83uyspaf75.jpg
Homework Equations
F=Kq1q2/r^2
E=kQ/r^2
The Attempt at a Solution
Answer choice E is not listed in screenshot, but states that there is no Net force on the Charge. I picked E, but I'm...
Homework Statement
Two charges, one of charge +1.5 x 10^–2 C and the other of charge –2.7 x 10^5 C, are 20.0 cm apart. The positive charge is to the left of the negative charge.
(a)Draw a diagram showing the point charges and label a point Y that is 5.0 cm away from the positive charge, on...
I'm having trouble trying to understand what a volt is, and I thought this question might be able to help me understand, so..
For example: If there are 10^6 electrons in one place, and 100 electrons in a different place, what will the potential difference between these two places be.
Also...
Homework Statement
Below is a graphic representation of the problem.
With a point charge at the origin, calculate the difference in potential of point B relative to point A using the path integral.
Homework Equations
As I recalled, to find the electric potential difference, Vab = - ∫ E ° dl...
When picturing electric fields, they are always based on a positive test charge. As you move on to potential difference and electrical currents, it is based more on electrons/negative charge. So, why aren't electric fields and fields lines based on a negative test charge instead of a positive...
Homework Statement
Hi!
I have a question about calculating electric field made by finite point charges
q_{1},q_{2},..., q_{n}.
From the book "introduction to electrodynamics", you can see that the electric field E at a point P made by the finite point charges can be calculated by the below...
The above equation gives the EPE of two point charges separated by a distance r.
Firstly, I do not understand how this formula gives the TOTAL EPE of the system.
Secondly, let's say I have three deuterium nuclei moving towards one another with initial speed V.
They all stop...
Homework Statement
Three point charges lie along a straight line as shown in the figure below, where q1 = 6.36 µC, q2 = 1.56 µC, and q3 = -1.84 µC. The separation distances are d1 = 3.00 cm and d2 = 2.00 cm. Calculate the magnitude and direction of the net electric force on each of the...
I did this problem just the way I took notes on it in class and keep coming up with the wrong answer. Please help I've spent nearly 2 hours on this one simple problem. Thanks.
Problem: Three point charges lie along a straight line as shown in the figure below, where q1 = 6.36 µC, q2 = 1.56 µC...
Hi,
I was studying Cherenkov radiation and here's what I read. A charged particle moving through a medium has an electric field. This is equivalent to the particle emitting photons which are absorbed by the atoms of the medium and causes them to reorient themselves.
I am a little...
Homework Statement
Two small spheres, each with mass m = 5.0 g and charge q, are suspended from a point by threads of length L = 0.30 m. What is the charge on each sphere if the threads make an angle θ = 20° with the vertical?
Homework Equations
F=k|q1q2|/r2
The Attempt at a Solution
I found...
Homework Statement
Charges Q, Q, and q lie on the corners of an equilateral triangle with sides of length a. Charge q lies on the top corner with Q and Q on the left and right corners.
(a) What is the force on the charge q?
(b) What must q be for E to be zero half-way up the altitudeat...
I hope this isn't in the wrong forum, it's not a problem, just a conceptual question for physics 2.
I have a few questions that I cannot find answer for in my physics book or online.
1) Why does moving a charge parallel to the magnetic field result in zero magnetic force?
Is this quality...
Homework Statement
see attachment
Homework Equations
The Attempt at a Solution
Do you see the step where they go from (1.35keq2)/a2
to 1.91keq2)/a2 ?
I can't get that step. To my mind. If you square 1.35 then take its square root, you get 1.35 not 1.91
Hey,
I have a question about the use of image charges to solve problems,
Once you have determined the potential of the problem by including image charges you have to check if the potential describes the physics properly,
so if you have an infinite earthed conducting sheet with chat q...
Hi, I'm an undergraduate biologist student. I was studying chemical bond, but, while trying to understand it, I couldn't really get what causes the electric charges, what seems essential to me. So, someone can explains, in the simplest way as possible, what is electric charge? What causes it...
Hello I need help with a problem: If I see two identical charges moving in the same direction parallel to each other with the same constant velocity, my intuition tells me that the magnetic field generated by their movemente will cause them to attract much like what happensa with two wires with...
Hi all
let suppose a charge is in oscillating (e.g antenna),it broadcast wave,and also suppose an observer oscillate , so the observer had saw the charge in fixed distance so we have not magnetic field.
what we could say about the energy that the observer recived?
Homework Statement
Two point charges are situated at A and B a distance of 35cm apart in a vacuum. The charge A is a positive charge of 16 μC and the field strength at X, a distance of 12 cm from A, is zero. Calculate:
(i) The field strength at X due to the charge at A. (I found this to be...
Hello to all, this may seem a very simple question but i can't work it out and have no clue where to start.
My question is: A 6v battery charges up a 470 microfarad capacitor in 1 second, what is the final charge of the capacitor? and what is the current while the capacitor is charging?
i...
A small charge of 4 x 10^-6 C is located at the point x=2 m, y=3 m in the xy-plane. A second small charge of -3 x 10^-6 C is at the point x=4 m, y=-2 m.
A) Calculate the force that the first charge exerts on the second. Express your answer in both terms of magnitude and angle, and also in i ...
I am trying to workout the drift of a charged particle from another particle using coulomb law. but the problem is the further the particles move, the less the force between them, so how can I work out the drift in such case?
We know that the force between two charged particles is:
F = (k Q1...
What cause a particle with the property of electric charge to interact with other charges?
My way of thinking is that due the natural isotropy of the electric field of the electric charges any other electric field near the charge would cause it to become anisotropic, thus causing acceleration in...
Electrostatics -- point charges and work
Homework Statement
A 3.0 μC point charge and a 9.0 μC point charge are initially infinitely far apart. How much work
does it take to bring the 3.0 μC point charge to x = 3.0 mm, y = 0.0 mm and the 9.0 μC point charge to x = -3.0 mm, y = 0.0 mm? (The...
I have the following formula on my formula sheet:
ΔU = U_a - U_b = q(V_a - V_b)
I was wondering if 'a' is final and 'b' is initial or is it the other way around? Also when I plug in my charge q into the formula, if it was a negative charge do I plug the negative sign into the formula? I...
Are both velocity and "jerk" of charges responsible for magnetic fields?
It is commonly believed that changes of electric fields cause contributions to a component of the magnetic field and that changes of magnetic fields cause contributions to a component of the electric field.
In the case...
Electric Field inside a closed gauss box.
Homework Statement
there are +2uC and -2uC charges inside a close "Gauss" box. Which of the following statement is true?
Homework Equations
given option are:
1) the net electric flux through the box is zero
2) the electric field is zero...
After I comb my hair, does it supposed that my hair is positively charged and the wood comb is negatively charged? since the electrons went from your hair to the wood comb.
Thanks in advance for any suggestions