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.
Homework Statement
Three point charges, which initially are infinitely far apart, are placed at the corners of an equilateral triangle with sides "b". Two of the point charges are identical and have charge "q".
If zero net work is required to place the three charges at the corners of the...
A Particle of charge q=7.5x10^-6 Coulombs is released from rest at .6m on the x axis. The particle moves due to charge Q = -20x10-6 C. What is the Kinetic Energy of the particle the instant it has moved .4 meters if Q stays fixed at the origin?
Here I used KE1 + U1 = KE2 + U2
Which equals 0 +...
I have some difficulties grasping the idea of this equation
Wp = q * E * r
Where
Wp - electrical potential energy
q - charge
E - the strength of the electric field
r - radius, or distance from the other point charge
So basically, say we have 2 point charges. One positive, and one...
Homework Statement
Calculate how much work it takes to make a square of side length A with point charges (all of charge q) at each vertex.
Homework Equations
The Attempt at a Solution
I know one way to do it. (find the difference in potential for each point and then go from there...
Homework Statement
A charge of 0.611 nC is placed at the origin. Another charge of 0.383 nC is placed at x1 = 8.1 cm on the x-axis.
At which point on the x-axis does this potential have a minimum?
Homework Equations
U=(kq1q2)/rThe Attempt at a Solution
I really have no idea how to even start...
Hi I'm having difficulty understanding why the solution for the answer to the following problem is worked out this way.
Three spheres are placed at fixed points along the x axis, whose positive direction points towards the right.
Sphere A is at x=47cm with a charge of 5x10-6C
Sphere B is...
Homework Statement
3 point charges are fixed in place in the right triangle shown below, in which q1= 0.67 microC and q2= -0.67 microC. What is the electric force on q3 with +1.0 microC due to the other two charges?
Magnitude?
direction, measured counterclockwise from the +x axis?
**HYP=10cm...
Q1. If two point charges have equal mass and and charg are released on a frictionless table, each has an initial acceleration (Ao). if instead you keep one fixed and release the other one, what will be its initial acceleration?Ao,2Ao or Ao/2?
Q2. A point charge of mass (m) and charge (q)...
Homework Statement
A point charge of -6 µC is located at x = 1 m, y = -2 m. A second point charge of 12 µC is located at x = 1 m, y = 3 m.
(a) Find the magnitude and direction of the electric field at x = -1 m, y = 0.
(b) Calculate the magnitude and direction of the force on an...
Hi all,
Here is my problem:
Two positive points charges are situated as the initial figure:
1/ How to compute the voltage between A and B (or C)?
2/ If the final condition is like described in the second figure, what is now the voltage between A and B.
3/ if the transition between the...
A fixed point charge of +2q is connected by strings to point charges of +q and +4q, as shown below. Find the tensions T1 and T2. (Use the following as necessary: q, d and k.)
For T1, I summed all the forces on each charge and got...
Consider the arrangement of two fixed point charges, equal in magnitude...
Consider the arrangement of two fixed point charges, equal in magnitude, shown in the figure.
Which of the following statements are correct for the initial motion of a third charge if it is released from rest in the...
Homework Statement
Three point charges are located at the corners of an equilateral triangle as in the figure below. Find the magnitude and direction of the net electric force on the 0.40 µC charge. (A = 0.20 µC, B = 6.60 µC, and C = -3.80 µC.). Diagram below...
Homework Equations
F=...
Homework Statement
The four point charges, each of + 3.00 μC, are situated at the corners of a rectangle of length, b = 60.0 cm and width, a = 30.0 cm.
Find the magnitude and direction of the force on q2, due to the other charges.
Solved this but i needed someone to check it for me because...
Homework Statement
i think i may have solved this but I am worried I am wrong because it seemed too simple. I wouldn't bother posting too check except that its for an assignment... the question is in the attachment- can someone please check this! Homework Equations
The Attempt at a...
Homework Statement
See attachment--please!
Homework Equations
F=kq1q2/r^2
The Attempt at a Solution
I can't see where to start this question, I can do questions where there is three point charges and it asks you to find the net force on one of them and i think that in essence this...
Homework Statement
Three equal point charges, each with charge 1.95 nanoC , are placed at the vertices of an equilateral triangle whose sides are of length 0.550m . What is the electric potential energy of the system? (Take as zero the potential energy of the three charges when they are...
Okay, in inertial reference frames, two particles with the same charge will always repel each other. Even if they were moving in parallel at high speeds, and thus producing magnetic fields, special relativity would come in and balance the forces from the electric and magnetic fields so that...
Homework Statement
I had this exam question for a final exam and I was wondering if I got it right or not. There are three point charges +4q equally spaced apart at the tips of an equilateral triangle with distance .11m apart from each other. What is the magnitude of the electric field at the...
Homework Statement
Two identical positive point charges Q are nailed down a distance 2D apart. Point P is midway between the two charges as shwon in the diagram. A dashed line is vertical i.e. perpendiculat to an imaginary line connecting the two charges a distance D from both charges...
Homework Statement
A point charge of +2.0 microC is separated from a second point charge of -0.35 microC by a distance of 4.0 x10-4 m. Calculate the size of the force that each charge exerts on the other and its direction. (Assume 1/4 pi ε0 = 9.0 x109 m F-1)
Homework Equations
F =...
Homework Statement
A proton has a velocity of 1.0 * 10^2 m/s in the x direction + 2.0*10^2 m/s in the y direction and is located in the z=0 plane at x=3.0m, y=4.0m at some time t=T. Find the magnetic field in z=0 plane at x=2.0m, y=4.0m.
Homework Equations
magnetic field is given by...
In an equilateral triangle a positive point charge +q is located at each of the vertices. If a 4th charge is added at the midpoint between one of the sides could this charge be such that the force on it would be zero?
Homework Statement
Two point charges are placed on the x axis. The first charge, q1= 8.00 , is placed a distance 16.0m from the origin along the positive x axis; the second charge, q2= 6.00 , is placed a distance 9.00m from the origin along the negative x axis.
Calculate the...
Homework Statement
A point charge q1:-4.00 nC is at the point x=0.600 meters, y=0.800 meters, and a second point charge q2:+6.00 nC is at the point x=600 meters, y=0 .
a) Calculate the magnitude of the net electric field at the origin due to these two point charges.
Express your answer in...
Edit: Apparently Coulomb's law only holds for electrostatics... in that case I understand that this problem is physically impossible. I'd still like to solve it if we assumed that coulomb's law did hold for moving charges
If there are two point charges that are initially separated by...
Homework Statement
A set of point charges is held in place at the vertices of an
equilateral triangle of side 10.0 cm, as shown in the figure (a) .
Find the maximum amount of total kinetic energy that will be
produced when the charges are released from rest in the
frictionless void...
Homework Statement
A charge of q1 = -8.5 μC is at y = 6.0 m, and a charge of q2 = -6 μC is at y = -4.0 m. Locate the point (other than infinity) at which the total electric field is zero.Homework Equations
E=k(q/r^2)
E1=E2
Quadratic Equation
The Attempt at a Solution
9x10^9 (8.5x...
Homework Statement
Three equal point charges, each with charge 1.00 microC, are placed at the vertices of an equilateral triangle whose sides are of length 0.200 m. What is the electric potential energy U of the system? (Take as zero the potential energy of the three charges when they are...
I am struggling to grasp the concept of the electric field between two opposite charges. I know that the field is strongest closest to the charge and gets weaker further away from the charge. I also know that the electric field lines go from positive to negative and that they are perpendicular...
Homework Statement
http://www.freeimagehosting.net/uploads/3e00ce8695.gif
Homework Equations
Electric field equation derived from Coloumb's Law (given on the screenshot above).
The Attempt at a Solution
Solution is given in the form of answer sheet...
Hi first post sorry if I didn't follow anyone specific rule. Me and my fiancee are stumped how my physics 2b teacher got 6kq^2/L^2 for F24. We understand that where r= L square root2/2 is squared so the result is L^2. But where in the heck did the 6 come from in 6kq^2.
[b]
1. The arrangement of charges shown in the figure is called a linear electric quadrupole. The positive charges are located at +-s. Notice that the net charge is zero.
Find an expression for the electric potential on the x-axis at distances y>>s.
Homework Equations
V= \sum1/4pi...
Homework Statement
Two point charges lie on the x axis. A charge of -2.5 µC is at the origin, and a charge of +8.5 µC is at x = 10.0 cm.
What is the net electrical field at points x = +4 and at x = -4?
Homework Equations
E = kq/r^2
The Attempt at a Solution
For x = +4...
E=...
A point particle that has a charge of 15.0 µC is located at x = 0, y = 0 (we'll call it q0 and a point particle that has a charge q is located at x = 12.0 cm, y = 0 (we'll call it q1. The electric force on a point particle that has a charge of 6.0 µC at x = 24.0 cm, y = 0 is -(19.7) N \hat{i}...
Homework Statement
A point charge q = 4.9 \mu C is placed at each corner of an equilateral triangle with sides 0.20 m in length.
Is the magnitude of the electric field at the center of the triangle greater than, less than, or the same as the magnitude at the midpoint of a side? Explain...
Homework Statement
*ignore the given numbers in the image, mine is different*
My numbers are:
Q1: 1nC
Q2: 8nC
Q3: -6nC
Homework Equations
E = \frac{kq}{r^2} * \hat{r}
The Attempt at a Solution
I only did (a1) so far. I know (a2) involves the exact...
Homework Statement
Four point charges are located at the corners of a square with sides of length a. Two of the charges are + q, and two are - q.
1)Find the direction of the net electric force exerted on a charge + Q, located at the center of the square, for the following arrangement of...
Homework Statement
Find positions of four charges in a plane (+1C, -1C, +2C, -2C) that result in an equilibrium (zero net force on each charge). Report positions as four (x,y) pairs.
Homework Equations
F = \frac{k_{e}q_{1}q_{2}}{r^{2}}
The Attempt at a Solution
I had no idea...
Homework Statement
A small sphere carrying a charge of q with mass m is suspended from point A by a massless thread of length L, as shown in the figure. A second sphere carrying a charge of 2q with mass M is suspended from a fixed rod from point B. The distance between A and B is equal to...
This is probably child's play for most of you, but a guy like me struggles to understand basic concepts. A kick in the pants to set me off in the right direction would be greatly appreciated.
Homework Statement
How far must the point charges q_1 = 7.60 microCoulombs and q_2 = -24.0...
Homework Statement
Four charges Aq,Bq,Cq, and Dq (q = 2.50 x 10-07C) sit in a plane at the corners of a square whose sides have length d = 69.5 cm, as shown in the diagram below. A charge, Eq, is placed at the origin at the center of the square.
DATA: A = 2, B = 8, C = 5, D = 4, E = -4...
Homework Statement
Two identical spheres with mass m are hung from silk thread with length L. Each sphere has the same charge, so q1=q2=q. The radius of each sphere is very small compared to the distance between the two spheres, so they may be treated as point charges. Show that if the angle...
Homework Statement
A point charge Q is located at the origin. The point charge produces an electric field at a radius of 2.0 meters from the origin of 20N/c.The electric potential of a spherical surface of radius 3.0 meters around the point charge is, in Volts.
Homework Equations...
1. b]1. Homework Statement
Two large metal plates are held tightly together. Two equal and opposite point charges are placed one each on either side of the plates, and equidistant from them. The line joining the two charges is perpendicular to the plane pf the plates.
What will happen when...
This is probably a product of how I was taught, but I am unsure of the status of conservation of energy in classical EM with point particles. Here is the background:
When I was taught in undergrad, general arguments were used to show that there needs to be a back-reaction on a point particle...
This is from Sadiku's Elements of electromagnetics. I have come to a result but it's different from that of the book.
Homework Statement
Three identical small spheres of mass m are suspended by threads of negligible
masses and equal length l from a common point. A charge Q is divided...
Homework Statement
A point charge Q is located on the axis of a disk of radius R at a distance b from the plane of the disk (Fig. below left). Show that if one fourth of the electric flux from the charge passes through the disk, then R = sqrt(3)b.
PLEASE SEE ATTACHED WORD DOCUMENT FOR...
Homework Statement
3 equal point charges on the vertices of a triangle. If the each of the charges are doubled, why is the resulting force on each charge quadrupled?
Homework Equations
F= Fx +Fy
F= kqk2/r^2
The Attempt at a Solution
I got doubled