What is Electric fields: Definition and 506 Discussions
An electric field (sometimes E-field) is the physical field that surrounds electrically-charged particles and exerts force on all other charged particles in the field, either attracting or repelling them. It also refers to the physical field for a system of charged particles. Electric fields originate from electric charges, or from time-varying magnetic fields. Electric fields and magnetic fields are both manifestations of the electromagnetic force, one of the four fundamental forces (or interactions) of nature.
Electric fields are important in many areas of physics, and are exploited practically in electrical technology. In atomic physics and chemistry, for instance, the electric field is the attractive force holding the atomic nucleus and electrons together in atoms. It is also the force responsible for chemical bonding between atoms that result in molecules.
Other applications of electric fields include motion detection via electric field proximity sensing and an increasing number of diagnostic and therapeutic medical uses.
The electric field is defined mathematically as a vector field that associates to each point in space the (electrostatic or Coulomb) force per unit of charge exerted on an infinitesimal positive test charge at rest at that point. The derived SI units for the electric field are volts per meter (V/m), exactly equivalent to newtons per coulomb (N/C).
Determine how far apart two parallel plates must be situated so that a potential difference of 2.50*10^2 V produces an electric field strength of 2.00*10^3 N/C
F=(k*Q1*Q2)/r^2
PD=kQ/r
E=kQ/r^2
I cannot even figure out which formulae to combine...
This isn't actually a homework problem. I just had a question about the solution they provided.
Homework Statement
2. Solution given in solutions manual
3. My question
When they convert dE into cylindrical coordinates why does the radius "a" lose its exponent?
dE =...
Homework Statement
In a cold plasma (neglecting thermal pressure) the background medium is motionless and uniform
for the electrons:
\rho_e = \rho_{e0} + \rho_{e1}
v_e = v_{e1}\hat{z}
where ρ is electron density and v is velocity. Subscript 0 denotes a constant value and 1 denotes a small...
If volumetric charge distribution has spherical symmetry
I want to find the trapped charge a in certain radius
Why did not need to do an integral from 0 to R to all the electric fields inside the sphere but take only the external field(how gauss law says)?
The Electric fiels is...
Homework Statement
Question: An electron and a proton are fixed at a separation distance of 925nm. Find the magnitude and direction of the electric field at their midpoint.
Homework Equations
E= Fe/q
The Attempt at a Solution
(8.988 x 10^9) x (q/(9.25 x 10^-7)2)
This is the...
A changing magnetic field creates a non conservative electric field. If the changing magnetic field is accelerating(2nd derivative in non-zero) the electric field must also be changing. Would this mean that the changing electric field is producing a magnetic field.
Depending on the order of...
Relationship between Electric Fields and Distance from point charge??
Homework Statement
Homework Equations
E= kq/r^2
The Attempt at a Solution
K so looking at the graph, I noticed that there is a inverse-square relationship between the electric field and the radius/distance...
I'm having a bunch of trouble with an electrostatics questions as well as an electric fields question. I'll start with the electrostatics problem.
Homework Statement
I am given the following equilateral triangle and asked to calculate the net electrostatic force on each charge...
I know this problem is simple enough but I can't get the hang of it
Find the electric field at point A in the diagram if (a) q1=2.00 μC and q2=3.00 μC. (b) q1=2.00 μC and q2= -3.00 μC.
Thank you.
P.S. If you can explain how you solved the problem that would be great. I'd really like to know...
Hi. My question is straightforward: how do I know when the charge inside a surface is zero?
I've read my textbook chapter twice, but it doesn't offer any explanation on this. In one example problem with a hollow shell, it simply makes the automatic assumption that "there's no charge inside...
The electrical system of typical thundercloud can be represented by a vertical dipole consisting of a charge of +40C at a height of 10km and a charge of -40C vertically below it at a height of 6km. What is the electric field at the ground directly beneath the thundercloud.
I am simply adding...
I have two questions that I cannot seem to figure out.
Homework Statement
1)A uniform electric field E=30 N/C exists parallel to the axis of a square pipe of side length l=5 cm as
shown in the figure. Calculate the total electric flux for the slanted face of the pipe
2) A very long metal...
So my physics textbook briefly mentions
What I don't understand is: If the paper is put between the charges, those charges would induce a dipole, right? Since there are charges on both sides and "like-charged" which way would the dipole point. The book says the tape is attracted to the paper...
Edit: This is my first post. This question isn't related to any homework problems but was inspired by my physics book. I apologize if this is the wrong forum but It seemed the right place based on the other posts.
So my physics textbook briefly mentions
What I don't understand is: If the...
Hello all,
I got this question off mastering physics and was unable to understand it. I eventually gave up to concentrate on other assignments and asked for the answer. I was unable to come up with more than one answer I thought possible without resorting to trial and error.
Answer: Vx,Vy,Vz =...
Homework Statement
The Electric field E produced by an unknown charge distribution p (rho) is E(r)= (constant)*((exp(-ar))/r^2)*(r_hat).
a.) Use Gauss' law in differential for to determine p(rho)
b.) Find the total charge q_tot by directly integrating p(rho), and show that it is 0.
c.)...
Three charged objects are arranged on a vertical line as shown
in the figure. The separation between charges is 3.0 cm.
a) If you wanted to find the force on charge C, which
fields would be relevant? Explain and calculate the
magnitude of this field. Which direction does it point?
b)...
Homework Statement
please see the pictures!
Homework Equations
F=k(q1)(q2)/r^2
The Attempt at a Solution
okay, I am just curious as to why t cos theta and mg are x components when they are clearly on the y axix!
I thought you used cos for x components and sin for y components
Homework Statement
lectric fields of varying magnitudes are directed either inward or outward at right angles on the faces of a cube, as shown in the figure.
What is the strength and direction of the field on the face F? (The cube does not contain any charges. Take EA = 13 N/C, EB = 26N/C...
Homework Statement
Have two electric fields.
\hat{x} E_1 e^{i(kz- \omega t)}
\hat{x} E_2 e^{i(-kz- \omega t)}
Where E_1, E_2 are real.
Sum them such that the result can be expressed as one magnitude and exponential, e.g., |E|e^(iq), Where E is real.
I have no clue how I would begin to...
I am having difficulty explaining this question to my student.
His solution to part ii was (taking r to be the distance between the point charges) E = 2(kQ/(r/2)^2 due to the fact that you are measuring the field strength half way between the point charges.
So, E = 2 x (9E9 x...
Homework Statement
We have a solenoid with current I and n turns per unit length and (neglecting hysteresis) a ferromagnetic core. Find B and H.
Show that when I is varied an electric field is induced and draw it on a diagram.
Homework Equations
\nabla \times E = - \frac{\partial...
I don't know, when given a point charge (sign is indicated = positive or negative), which direction the field lines go
Although I NOW know that if the point charge is positive, field lines are outwards, and if negative then they are inwards...HOWEVER, I have come across an example or two...
3. Two electrons are fired at 3.5x10^6 m/s directly at each
other.
(a) Calculate the smallest possible distance between the
two electrons.
(b) Is it likely that two electrons in this situation will actually
get this close to each other if the experiment is
performed? Explain your answer...
Homework Statement
An negatively charged sphere of mass 3.3x10^-15 kg is held at rest b/w two parallel plates separated by 5.0mm when the potential difference between them is 170V. How many excess electrons are on the sphere?
B) The charged sphere suddenly loses one of its excess electrons...
Homework Statement
Find the electric field for a point in the center of a square, +45microC on one corner and -27microC on the other 3
Homework Equations
E = (kQ1)/r2
The Attempt at a Solution
I know how to do the Electric field equations in a straight line, but for a square...
lets say i have a simple battery circuit
1) why is the static electric field ,produced by the potential difference of battery, parallel to the wires? shouldn't it be pointing radially outwards? (for +ve)
2) is the electric field inside the wire or outside the wire? if its outside, then how...
Homework Statement
Two large conducting sheets are charged with a positive surface charge density. They stand vertically facing each other a distance d apart.
a.) suddenly, we shrink the left sheet to a square with sides equal to d, what is the field at the point along the central axis of...
Homework Statement
This is a concept question on a study guide I came across and I really didn't know how to answer it or think about it...I havn't seen anything like this question before
How could you prepare a spherical chamber that has a uniform electric field everywhere inside?
A 9v battery is connected across 2 parallel plates separated by 3mm.
a. what is the magnitude of the electric field between them?
b. the plates have an area of .5m^2, how much charge can be stored?
c. how much energy can be stored?
please help me with this question. i am lost and...
I am confused about electromagnetic fields. I am fine with the ideas of how photons are emitted from an object (whether through electron excitation or nuclear fusion) and I understand that any electromagnetic radiation contains an electric field as well as a magnetic field, but I am having...
Homework Statement
A small charged bead has a mass of 1.0 g. It is held in a uniform electric field E= 200,000 N/C up. When the bead is released, it accelerates upward with an acceleration of 20 m/s^2. What is the charge on the bead?
Homework Equations
F= qE
F= mg
(possibly F= ma)...
Homework Statement
An electron has a velocity of 1.90 km/s (in the positive x direction) and an acceleration of 2.00 E12 m/s^2 (in the positive z direction) in uniform electric and magnetic fields. If the electric field has a magnitude of strength of 20.0 N/C (in the positive z direction)...
Lets say you have a hollow sphere, which is a conductor, and you put some charge on it. I understand why the electric field inside the sphere is 0, but I don't see why the electric potential V is constant.
Could someone explain?
Thanks
Homework Statement
We are given a picture like the one I attached, in the question we are told that ATLEAST 2 are positive which one (if any) is negative
a) Only A
b) Only B
c) Only C
d) None of them
Homework Equations
None really all you need to know is that when the lines are...
Homework Statement
A hollow ball of radius 5 cm, made of very thin glass, is rubbed all over with a silk cloth and acquires a negative charge of -9.5e-08 C which is uniformly distributed all over its surface. Location A, shown in the diagram, is inside the sphere, 1 cm from the surface...
Homework Statement
In my electromagnetics book, in the section that talks about loss tangents, the equation for average power dissipation per unit volume is P=(1/2)*J*E (W/m^3). What does the coefficient of 1/2 come from? Earlier in the book, it gave the differential power dissipation dP=...
Homework Statement
This isn't about a specific problem, but it is based off of a homework problem. There is an insulating sphere (from radius 0 to a), and it is concentric with a spherical conducting shell (from radius b to c). If I know the charge of the insulating sphere and the net charge...
Consider three very large, parallel planes of charge that are equally spaced as shown in the figure below. These planes are insulators, and each is charged uniformly with +188 µC on every square centimeter of area on the top surface of each plane. Use Gauss's law to determine the field at points...
Hello
I have just read first five chapters from Feynman's "Lectures on Physics Vol. 2"
on electromagnetism and couldn't find satisfactory answer to my question, so I am posting this question.
Its claimed that electric field inside a "perfect conductor" (something with unlimited...
Homework Statement
A cylinder of radius r is surrounded by a concentric cylinder of inner radius Ra and outer radius Rb. The inner cylinder has a charge density lambda (charge per unit length) and the concentric cylinder has no net charge. I have to find the electric fields:
a)inside the...
Homework Statement
I'm currently doing Physics 12.
Its about electric fields, voltage, current, power, gravitation field and series, parallel and series-parallel circuits.
I've already taken the test once and got 48% because I didn't fully study the last section which involved...
Homework Statement
Three charges, q1 = +2.10 10-9 C, q2 = -3.09 10-9 C, and q3 = +1.08 10-9 C, are located on the x-axis at x1 = 0, x2 = 10.0 cm and x3 = 20.0 cm. Find the resultant force on q3.
I am unsure of how to even attempt this problem...
If a sphere has a net charge of zero, then it experiences no electric field right? But if you bring a + charged rod it, the electrons experience a field and all move towards it. But the net charge for the sphere is still zero since same number and electrons cancelling out. So do we say the...
Homework Statement
Comment on the electric field lines of a pair of finite parallel plates (a) between the plates and (b) near the edges of the plates.
Homework Equations
The Attempt at a Solution
Homework Statement
A charge +q of mass m is free to move along the x axis. It is in equilibrium at the origin, midway between a pair of identical point charges, +Q, located on the x axis at x = +b and x = -b. The charge at the origin is displaced a small distance x << a and released. Show that...
Homework Statement
Why is this answer saying that Ea > Eb?
Homework Equations
Everything pertinent to this question is located in this picture:
http://img94.imageshack.us/img94/1187/ch22q9part1.png
[PLAIN]http://img94.imageshack.us/img94/1187/ch22q9part1.png
The question is...
Homework Statement
A point charge +Q is surrounded by a spherical shell of inner radius a and outer radius b. The spherical shell has charge density \alphar.
a) What is the electric field for r < a?
b) What is the electric field for a < r < b?
c) What is the electric field for r > b?
d)...
Two small spheres, each of mass 4.00 g, are suspended by light strings 10.0 cm in length. A uniform electric field is applied in the x direction. The spheres have charges equal to -2.00 multiplied by 10^-8 C and +2.00 multiplied by 10^-8 C. Determine the electric field that enables the spheres...
Homework Statement
A π- ("pi-minus") particle, which has charge -e, is at location ‹ 5.00e-9, -5.00e-9, -6.00e-9 › m. What is the electric field at location < -5.00e-9, 3.00e-9, 5.00e-9 > m, due to the π- particle?
5e-9 is equivalent to 5*10^-9
Homework Equations
E=(k*q/r^2)r-hat...