What is Point charges: Definition and 359 Discussions
A point particle (ideal particle or point-like particle, often spelled pointlike particle) is an idealization of particles heavily used in physics. Its defining feature is that it lacks spatial extension; being dimensionless, it does not take up space. A point particle is an appropriate representation of any object whenever its size, shape, and structure are irrelevant in a given context. For example, from far enough away, any finite-size object will look and behave as a point-like object. A point particle can also be referred in the case of a moving body in terms of physics.
In the theory of gravity, physicists often discuss a point mass, meaning a point particle with a nonzero mass and no other properties or structure. Likewise, in electromagnetism, physicists discuss a point charge, a point particle with a nonzero charge.Sometimes, due to specific combinations of properties, extended objects behave as point-like even in their immediate vicinity. For example, spherical objects interacting in 3-dimensional space whose interactions are described by the inverse square law behave in such a way as if all their matter were concentrated in their centers of mass. In Newtonian gravitation and classical electromagnetism, for example, the respective fields outside a spherical object are identical to those of a point particle of equal charge/mass located at the center of the sphere.In quantum mechanics, the concept of a point particle is complicated by the Heisenberg uncertainty principle, because even an elementary particle, with no internal structure, occupies a nonzero volume. For example, the atomic orbit of an electron in the hydrogen atom occupies a volume of ~10−30 m3. There is nevertheless a distinction between elementary particles such as electrons or quarks, which have no known internal structure, versus composite particles such as protons, which do have internal structure: A proton is made of three quarks.
Elementary particles are sometimes called "point particles", but this is in a different sense than discussed above.
If these point charges were placed in vacuum without any spherical shells in the picture, then the force between these charges would be ##F =\dfrac { k q_1 q_2} {d^2}##.
But, I am unable to reason how spherical shells would alter the force between them.
I do know that if charges were on the...
I tried using the distance between r2 and r1 and plugging them into the equation for i, j, k. >>
So for the force in the x direction it was k*(4E-6*4E-6)/(4-9)^2. The answer I got was wrong according to webassign. Can someone please tell me what I am missing?
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 I am pretty sure about this far but I am struggling to calculate the X-axis intensity and Y-axis intensity to find the entire approximate intensity with the...
Let's speak in the classical context (non quantum). We assume that point charges move in a conductor following Newtonian mechanics. How do point charges move along the boundary of the conductor and how do they stop (equilibrium) in the end?
So, i was trying to calculate, the net force between 2 point charges in their rest frame, and in a frame where they are moving.
So, assume, there are 2 point charges each of charge +q.
They are r distance apart from each other and moving parallel to each other with a speed v relative to a lab...
So this is more of an intuitive question rather than a mathematical one. I present the problem.
Assume I have 2 charges of charge +q at a distance r from each other on the z axis. Position of two charges is (0,0,r/2) and (0,0,-r/2). Assume now that I want to calculate the force these two...
I traced a spherical X-ray Gaussian (green) where the negative charges were diametrically opposite. My question is this: I can transform the entire charge of the Gaussian sphere into a point charge placed in the center. So, can I analyze only the electrical forces of the two negative charges...
I need some help resolving the follow problem. I really don't know where to put the "twice as large as the resultant force on Q3" in order to build an equation.
Thank you !
Below is the work I've attempted. I used 2 PE b'c there were 2 point charges, and only one KE b'c only the proton is moving. The final equation in case it's hard to see is V(esc) = sqrt (4kQq / mr).
I'm not sure if I did it right. Did I set up this equation right? and I am also not sure what...
Using superposition and "breaking up" the vectors into three components ax, ay, az on points should solve the task.
For Q1 there is no effect on x-axis.
On the y-axis the distance from Q1 to origin is 2. Using coulombs law will give us -> (-Q/4) * k , where k is the constant 1/(4*pi*e0).
On...
I am stuck on the following question (Image attached of my work) appears to make sense until i try to take a limit as c--->0 because the result should be 0. Am i missing something, if so can't you point me in the right direction.
Thank you
Summary: Potential at origin of an infinite set of point charges with charge (4^n)q and distance (3^n)a along x-axis where n starts at 1.
From V=q/r, we find Vtotal=sum from 1 to infinity of (4/3)^n(q/a), which diverges. There cannot be infinite potential because there is a finite electric...
An electric dipole is a system of two opposite point charges when their separation goes to zero and their charge goes to infinity in a way that the product of the charge and the separation remains finite.
Now how can we have a continuous electric dipole volume distribution from such a...
A charge Q is placed at the centre of the square of side 2.90 cm, at the corners of which four identical charges q = 6.5 C are placed. Find the value of the charge Q so that the whole system is in equilibrium. Can someone help me figure out where I have went wrong, I began by finding the force...
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, the...
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...
Homework Statement
A point charge q1=15.00μC is held fixed in space. From a horizontal distance of 8.00 cm , a small sphere with mass 4.00×10−3kg and charge q2=+2.00μC is fired toward the fixed charge with an initial speed of 40.0 m/s . Gravity can be neglected.
What is the acceleration of the...
I wrote and solved this problem but am having serious doubts about the answer I obtained.
Homework Statement
Two point charges \pm q move along the z-axis with velocity \pm v. If they are at the origin when t=0, what is the electric field magnitude a distance r from the z-axis?
Homework...
Homework Statement
"Can you arrange the two point charges q1 =−2.0×10−6 C and q2 =4.0×10−6 C along the x-axis so that E =0 at the origin?"Homework Equations
E = K (|q|/r2)
K = Coloumb Constant
The Attempt at a Solution
Since one particle is negatively charged and the other is positively...
Homework Statement
Find the potential at points P1, P2, P3, and P4 in the diagram due to the two given charges.
Homework Equations
VP =k∑qi/ri
p = q ⋅ d
The Attempt at a Solution
I'm not sure how to approach the problem. I thought about using that given equation four times and adding it all...
Homework Statement
Two positive charges q1 = q2 = 2.0 μC are located at x = 0, y = 0.30 m and x = 0, y = -0.30 m, respectively. Third point charge Q = 4.0 μC is located at x = 0.40 m, y = 0. What is the net force ((a)magnitude and (b)direction) on charge q1 exerted by the other two charges...
Homework Statement
"Let there be two point charges ##q_1=3.5μC## and ##q_2=-3.5μC## located at ##(0,0.3 m)## and ##(0,-0.3 m)## respectively. What force do these two charges exert on a test charge ##Q=4.5μC## at ##(0.4 m,0)##?"
*title should read "due to two point charges"* <Moderator's note...
Homework Statement
Two spherical point charges each carrying a charge of 40 mC are attached to the two ends of a spring of length 20 cm. If its spring constant is 120 Nm-1, what is the length of the spring when the charges are in equilibrium?
Homework Equations
1) F = k*(q^2)/r^2 where k is...
Homework Statement
Three point charges each carrying a charge of 11.0 µC are located at the corners of an equilateral triangle of side 15.0 cm. Calculate the magnitude and direction of the force on each charge.
Homework Equations
k = 9.0x109NM2C-2
F = k⋅(Q1⋅Q2)/r2
The Attempt at a Solution...
Suppose a charge q is placed at point x=0, y=0. A second charge q is placed at point x=8.0m, y=0. What charge must be placed at the point x=4.0m, y=0 in order that the field at the point x=4.0m, y=3.0m be zero?
Hello! So this is going into physics because it is a physics problem, but it is maths that is the real problem. So if you came here to help someone with physics and not maths I'm sorry.
1. Homework Statement
Find the force of repulsion between two point charges of +1C and +3C if they are...
I came upon this:
http://physics.stackexchange.com/questions/174514/will-the-electrostatic-force-between-two-charges-change-if-we-place-a-metal-plat/323006#323006
question on Physics Stackexchange which I found very interesting.
The configuration is basically two positive point charges q and...
Homework Statement
Two m = 4.0 g point charges on 1.0-m-long threads repel each other after being charged to q = 80 nC , as shown in the figure. What is the angle θ? You can assume that θ is a small angle.
Homework Equations
Fe=kq2/r2
F=ma
Fg=mg
The Attempt at a Solution
Equation 1:[/B]
r =...
Why does the electric field strength on a straight line (E = k.(Q1/d12+Q2/d22). D1,2 = distance with respect to Q1,Q2) between two point charges vary with the location on this line while the field strength between two parallel plates which remains the same anywhere between the plates...
Homework Statement
[/B]
Derive expressions for the magnitude and direction of the electric field at point P and the potential
at R.
Charges Q1 and Q2 are both positive.
Distance from Q1 to P is h, distance from Q2 to P is √2 h
Homework Equations
E = k q/r^2
The Attempt at a Solution
I...
Homework Statement
What is the direction of the force F on the -10 nC charge in the figure? Give your answer as an angle measured cw from the +x-axis.
Express your answer using two significant figures.
Homework Equations
##F = k\frac{Qq}{r^2}##
The Attempt at a Solution
I started by getting...
Homework Statement
Two point charges are placed on the x axis. The first charge, q1 = 8.00 nC , is placed a distance 16.0 m from the origin along the positive x axis; the second charge, q2 = 6.00 nC , is placed a distance 9.00 m from the origin along the negative x axis.
Photo shown by...
Homework Statement
In an experiment modeling point charges I had to find equipotential lines. I did so using a voltmeter. The results looked like this:
Not a good quality picture, but the equipotential line on the right says 1.3 mV and the one on the left says 2.3mV. From this I had to...
Homework Statement
Find the interaction energy ( ##\epsilon_0 \int \vec{E_1}\cdot\vec{E_2}d\tau##) for two point charges, ##q_1## and ##q_2##, a distance ##a## apart. [Hint: put ##q_1## at the origin and ##q_2## on the z axis; use spherical coordinates, and do the ##r## integral first.]Homework...
Homework Statement
Hi,
The question is
"
Three point charges (q,−2q,q) are located in a straight line with separation a and with the middle charge (−2q) at the origin of a grounded conducting spherical shell of radius b ..."
I have found a solution for this problem but there is one step that...
Hi,
I am trying to understand how light momentum transfers between point charges. I have a few questions if you could help me find some answers or direct me to some sources.
Situation #1
Electron/Wire - There is an electron at rest light years away from a wire that has AC flowing thru it...
Homework Statement
Two particles each with a charge of +3.00 μC are located on the x axis, with one particle at x = -0.80 m, and the other particle at x = +0.80 m.
a) Determine the electric potential on the y-axis at the point y = 0.60 m.b) What is the change in electric potential energy...
Hello, I've been trying to answering this question but my answer is always wrong.
Two point charges, -9.10 μC and 21.29 μC, are placed at x = 0 cm and x = 8.00 cm, respectively.
(a) At what point along the x-axis is the electric field zero?
What i did: i figured that the point should be on the...
Homework Statement
There are three point charges inside a conducting spherical shell of radius R. One of them of charge -2q is in the origin and the other two with charge q are in z=d and z=-d. Find the potential inside the sphere!
Homework Equations
##\nabla^2\phi=4\pi \rho##
3. The attempt...
Find the force on 2Q and -Q/22. Force between two point charges is given by : F = k.q1.q2 / d[2][/SUP]The Attempt at a Solution
To find the force on 2q, I added the charges on left side and then calculated it using the formula.
But how do we do it for -Q/2.
Please guide me. Thanks
At the outset, I want to explain that this is a problem I came up with myself. It's not actually homework, and I suspect it is deeply conceptually flawed in some manner that I have yet to determine.
1. Two point charges of like polarity, ## q_1 = q_2 = 1C ##, start out separated by distance ##...
Homework Statement
1. Compute the electric field vector at the position of charge B for the case where q_{A}=4q_{C} and r_{1}=2r_{2}
2. Suppose that all three charge are positive and that q_{A}=4q_{C} . Consider the case where f q_{B} is moved to the right by a distance dr.
Now r_{1} = 2r+dr...