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
Two point charges are placed on the x axis. The first charge, q1= 8 nC, is placed a distance 16m from the origin along the positive x axis; the second charge, q2= 6 nC , is placed a distance 9m from the origin along the negative x axis.
Find the electric field at the...
Homework Statement
Two point charges q and 4q are distance L apart and free to move. A third charge is placed so that the entire three-charge system is in static equilibrium.
Homework Equations
\SigmaF=0 This is the equation for static equilibrium
\vec{E}=q/4\pi\epsilon_{0}r^2
The...
Homework Statement
What are the strength and direction of the electric field at the position indicated by the dot?
Part A:
Give your answer in terms of the horizontal and vertical components, separated by commas. Take the positive directions to be up and to the right.
Part B:
Specify the...
Question
Charges at three corners of a square are shown in Figure P26.34, in which n = 9. To answer the following questions, use the letters k, Q, q, L, and m.
IMAGE IS LOCATED HERE: http://www.webassign.net/knight/p26-34.gif
a) Write the electric field at point P in component form.
b)A...
Homework Statement
Six point charges, four positive (+q) and two negative (-q), are fixed at thepositions shown (i attached a .gif file --pls tell me if this isn't visable) in the x-y plane; q = 2.1 × 10-6C and a = 0.93 m. A test charge Q = 0.6 × 10-6C is at the origin.
(a) Find the x- and...
Homework Statement
A point charge q_{1} = 4.15 \times 10^-6 is located on the x-axis at x = 1.80 m, and a second point charge q_{2} = -5.80 \times 10^-6 C is on the y-axis at y = 1.10 m. What is the total electric flux due to these two point charges through a spherical surface centered at...
Homework Statement
Two charges Qa = 3 µC and Qb = -3 µC are placed on the x-axis with a separation of a = 21 cm.
(a) Find the net electric field at point P, a distance d = 13 cm to the left of charge Qa.
This is no prob = -1364069.13N
(b) Find the force on Qb due to Qa .
No prob...
Homework Statement
Two identical charges q are placed on the x axis, one at the origin and the other at x = 5 cm. A third charge -q is placed on the x-axis so the potential energy of the three-charge system is the same as the potential energy at infinite separation. Its x coordinate is: (x=13)...
For two point charges of the same charge (positive) that are placed a distance from each other "r", the electric field in the midpoint of r is zero.
Now here's my question, what if one point charge had double the charge of the other? At what point between the two charges the electric field...
Homework Statement
There are three charges on the x-axis labled q1 = 9.9 uC, q2= -5.1 uC, q3 = ?
The distance between q1 at the origin and q2 is 0.1 m, what is the equilibrium distance between q3 and q1, and does that distance depend on the polarity of q3 ?
Homework Equations
F =...
Identical 8-μc point charges are positioned on the x-axis at x=+/-1.0m and released from rest simultaneously. What is the kinetic energy of either of the charges after it has moved 2.0m?
some relevant formulas are:
E=kq/r^2
V=-Ed
V=U/q
my attempt at the question:
i started by finding...
Three point charges with a distance a between them (as shown). What is the resultant force on q1?
Is this correct or am I doing this completely wrong?
edit: that should be Q1 multiplied by Q3 not adding
http://img513.imageshack.us/img513/3668/untitledxr7.jpg
Homework Statement
One particle has a mass of 3.00 10-3 kg and a charge of +7.50 µC. A second particle has a mass of 6.00 10-3 kg and the same charge. The two particles are initially held in place and then released. The particles fly apart, and when the separation between them is 0.100 m...
Two point charges are located on the x−axis: a charge of +7.80 nC at x = 0 and an unknown charge q at x = 0.50 m. No other charges are nearby. If the electric field is zero at the point x = 1.0 m, what is q?
I separated the charges.
q1 = +7.80 nC
q2 = unknown
I am confused about the...
Hey all this question appeared on my last assignment that was due on friday and had me completely stumped for the entire week and well still does, i couldn't even get off the ground (im not very good with these algebra questions) . anyway in the interests to doing my very best on my midterm exam...
Homework Statement
Positive point charges q_1= 6.90 microC and q_2= 2.90 microC are moving relative to an observer at point P as shown in the figure. The distance from the observer to either charge is originally d = 0.190 m.The two charges are at the locations shown in the figure. Charge...
Hi,
I'm currently taking first year physics in university and I have an online assignment due tonight. Due to it being saturday, I cannot contact any of the TAs or professors for help, and my friends and I are stumped.
I had 15 tries at answering this question and now I only have 2 left...
Two point charges are separated by a distance r and repel each other with a force F. If their separation is reduced to 0.280 times the original value, what is the magnitude of the force of repulsion between them?
I don't really understand this question and don't know where to start.
Would...
What are the magnitude and direction of the electric field midway between two point charges, −14.0 µC and +13.0 µC, which are 7.40 cm apart?
I used the F = ((k)(q1)(q2))/r^2
F= ((9x10^9)(-14)(13))/(7.40^2))
F= 2.99 x 10^10
however that answer is wrong. (The correct answer is...
For the life of me I can't seem to get this problem.
An electrically neutral model airplane is flying in a horizontal circle in a 3m guideline, which is nearly parallel to the floor. The line breaks when the Kinetic energy is 50J. Now, reconsider the same situation, except now there is a point...
Homework Statement
Two point charges lie on the x axis. A charge of +8.4 µC is at the origin, and a charge of -3.8 µC is at x = 10.0 cm.
At what position x would a third charge q3 be in equilibrium?
Homework Equations
F=(kq1 q2)/r^2
The Attempt at a Solution
I think that my main...
Hi,
Homework Statement
Two point charges 2.0 cm apart have an electric potential energy -149.9 µJ. The total charge is 28 nC. What are the two charges?
Homework Equations
U = (kqQ) / r
The Attempt at a Solution
U = -149.9 x 10^-6 = [(9 x 10^9)(28 x 10^-9 - q)(q)] / (0.02)...
"The net flux through ANY closed surface surrounding a point charge q is given by q/"permittivity of free space" and is independent of the shape of that surface."
I'm having a little trouble understanding this... when my book derived this formula, it did so by using the surface area of a...
Hello,
I am doing electrostatics at the moment and have difficulties to solve the following problem. Any hint that helps me to find the answer will be appreciated!
"On every corner of a square are movable point charges with the charge of 'q'. Where does a fifth movable point charge have to...
I am having a little trouble knowing how to approach the following question:
Twi point charges q and -q are placed 2d apart. Show that a conducting sphere of small radius r (where r << 2d) is placed midway between the charges, show the force on each is increased by a factor of approx (1 +...
Problem:
A charge of +18 uC is on the y-axis at y = +3.0m. A charge of -12 uC is at the origin. Last, a charge of +45 uC is on the x-axis at x = +3.0m. Determine the magnitude and direction of the net electrostatic force on the charge at x = +3.0mm. Specify the direction relative to the...
I've been working on the following problem but when I try my answer online, it keeps coming up as incorrect. A charge Q1=-9.4 C is 4.8 m from a charge Q2 = 3.6 C. What is the magnitude of the electrostatic force on Q1?
I'm pretty sure for this its just Coulomb's Law so:
F = (k(Q1*Q2))/r^2
F...
Here is the problem:
Three point charges are aligned along the x-axis as shown below. Find the electric field at the position x = +2.0m, y=0.
........y
........|
--------|<--.50m --->|<--------------.80m-------->|
--------0------------0-----------------------------0--------- X...
A point charge q is a distance d from a grounded conducting plate of infinite extent (figure a). For this configuration the potential V is zero, both at all points infinitely far from the particle in all directions and at all points on the conducting plate. Consider a set of coordinate axes with...
I'm working on the following problem:
The drawing shows four point charges. The value of q is 2.0 µC, and the distance d is 0.74 m. Find the total potential at the location P. Assume that the potential of a point charge is zero at infinity...
Difficulties with dipoles & point charges...
Help would be appreciated a lot with the following problems:
~ A positive point charge +Q is at the origin, and a dipole of moment p is a distance r away (r>>L) and in the radial direction as shown below...
suppose there existed 3 point charges with known charges and separating distances. I know you can determine the total potential of the system by using one charge as a reference (give it a potential of 0J), calculate the potential of another charge with respect to that charge (x J), and then...
A point charge q_1=-4.00\;{\rm nC} is at the point x = 0.600 m, y = 0.800 m, and a second point charge q_2=+6.00\;{\rm nC} is at the point x = 0.600 m, y = 0.
Calculate the magnitude of the net electric field at the origin due to these two point charges.
Can somebody please check over my solution. I cannot figure out what's wrong. My final answer is not right. I think I may have an error with the signs of the point charges or may have a dumb calculation error.
Thank youFour point charges, fixed in place, form a square with side length d.
The...
Hello!
Just hoping for a bit of help on a homework problem I'm doing at the moment...
Basically this is the question:
Three point charges are placed along the y axis: a charge q at y=a, a charge -2q at the origin and a charge q at q=-a. Such an arrangement is called an electric...
A point charge q =-4.00 nC is at the point x = 0.600 m, y = 0.800 m, and a second point charge q=6nC is at the point x = 0.600 m, y = 0.
A)Calculate the magnitude of the net electric field at the origin due to these two point charges.
I assume i can just treat the electric field charge...
A point charge q1 -4 nC is at the point x = 0.600 m, y = 0.800 m, and a second point charge q2 +6 nC is at the point x = 0.600 m, y = 0.
I need to calculate the magnitude of the net electric field at the origin due to these two point charges.
|...
How much voltage must be used to accerlerate a proton (radius 1.2E-15 m) so that it has sufficient energy to just penetrate a silicon nucleus? A silicon nucleus has a charge of +14e, and its radius is about 3.6E-15 m. Assume the potential is that for point charges.
Heres another similar question:
Two point charges, q1= 0.50 x 10^-9 C and q2= 8.00 x 10^-9 C are seperayed by a distance of 1.20 m. At what point along the line joining the points charges, is the total electric field die to the two charges equal to zero?
Two positive point charges q are located on the y-axis at +-(1/2)s. Find an expression for the potential along the x-axis.
Express your answer in terms of epsilon_0, pi, q, x, and s.
for this one, i know V = (1/4*pi*epsilon_0)*q/r.
so i was thinking its just like finding the potential of...
Three point charges are arranged at the corners of a square of side L. What is the potential at the fourth corner (point A), taking V = 0 at a great distance?
OK, I am very confused. First of all, Giancoli (my textbook) seems to explain how to do this for one point charge, but I am confused...
As shown below, an infinite number of point positive charges of 8.0 C are placed on the x-axis at x=a, 2a, 4a, 8a, ... with a=18 cm. Find the electric potential (in V) at the point x=0.
0---a----2a---4a-----8a-------
Ok so I'm using the equation V=1/(4piEpsilon)Sigma(q/r). and it's not...
The question and detail:
I setup the problem using energy conservation: K_a + U_a = K_b + U_b:
K_a = total kinetic energy of the 3 charges when they're at rest
U_a = total potential energy of the 3 charges when they're at rest
K_b = total kinetic energy of the 3 charges when they're far...
Given are two charges +1 X 10^-6 and one 3 X 10 ^ -6 distnace of 10 cm apart
I know there is a poitn in between these two and it is 4 cm from the 1.0 X 10^-6 charge
But i am asked to plot the elctric field strength as a function
if the elctric field is pointing right, then positive...
http://eastvan.bc.ca/~kim/phys.jpg
Four identical charges Q+ occupy the corners of a square with sides of length a. A fifth charge, q, can be placed at any desired location. Find the location of the fifth charge, and the value of q, such that the net electric force acting on the original...
I need help for the following problem:
Two alpha-particles (diameter 1.9 x 10^-19 m) are headed directly toward each other with equal speeds. Compute the minimum energy in electron volts each particle must have if they are to collide. What inital speed must each particle have?
For the...
An electron starts at the position (0,0) with an initial velocity 5,000,000 m/s at 45 degrees angle to the x axis. THe electric field is in the positive y direction and has a magnitude of 35000 N/C. At what location will the electron strikes?
Please help me setup this problem.
:confused:
A point charge of -.70microC is fixed to one corner of a square. An identical charge is fixed to the diagonally opposite corner. A point charge q is fixed to each of the remaining corners. The net force acting on either of the charges q is zero. Find the magnitude and algebraic sign of q...