# Help approximating an electric field between points.

• Sheolfire
In summary: What is the approximate electric field at A due to piece 2?The Attempt at a SolutionI did K * Q which is (9 * 10^9)* ((5/3) * 10 ^ -9)) which comes out to 15. Then I attempted to find r^2, which I believe would be (.02^2 + .13^2) and do 15 / .0173. Then I tried to multiply by the unit vector r <.98837, .15205, 0> to get <856.9697, 131.6415, 0> as my answer. I'm guessing there's some problem with how I'm calculating the r values since when
Sheolfire

## Homework Statement

A strip of invisible tape 0.13 m long by 0.019 m wide is charged uniformly with a total net charge of 5 nC
(nano = 1 ✕ 10−9)
and is suspended horizontally, so it lies along thex axis, with its center at the origin, as shown in the figure below. Calculate the approximate electric field at location

0, 0.02, 0

m (location A) due to the strip of tape. Do this by dividing the strip into three equal sections, as shown in the figure below, and approximating each section as a point charge. (Assume each point charge is located at the center of the section it approximates. Express your answer in vector form.)
http://prntscr.com/9xvusu picture of the tape.

(a) What is the approximate electric field at A due to piece 1?

E = kq/r^2 rhat

## The Attempt at a Solution

I did K * Q which is (9 * 10^9)* ((5/3) * 10 ^ -9)) which comes out to 15. Then I attempted to find r^2, which I believe would be (.02^2 + .13^2) and do 15 / .0173. Then I tried to multiply by the unit vector r <.98837, .15205, 0> to get <856.9697, 131.6415, 0> as my answer. I'm guessing there's some problem with how I'm calculating the r values since when I did part b (b) What is the approximate electric field at A due to piece 2?
it worked, but I was only managing the y component (.02m) since it was right below point A.

Last edited by a moderator:
There would be something wrong with how you are handling the x component then?
First, what did you get for the location and size of each of each point charge used in the approximation.

I see you have put the end charges a distance 0.13m from the center ... considering that the strip is only 0.13m long, that puts the end charges off the ends of the strip.
You should sketch the layout - the strip is centered on the origin so it cannot extend more than 0.13/2 m to either side.
Mark off the boundaries of the 3 sub-strips. Where is the logical place to put the point charges?
Hint: not at the ends of the strip.

Sheolfire
I tried using (15/2 * (1/3) ) as my distance (.02166) and ended up with something that seems closer, but it still not right. I did 15 / (.02^2 + .0266^2) = 17252.396 and then found rhat again with .0266/.02949 and .02/.02949. I ended up getting <12677.12, 11701.96, 0>.

Nevermind, I figured it out, it should be .13/2 * 2/3 not 1/3. Thanks for the help.

Well done.

## 1. What is an electric field?

An electric field is a physical field that surrounds an electrically charged particle or object. It is responsible for the forces experienced by other charged particles or objects in its vicinity.

## 2. How is an electric field measured?

An electric field is measured in units of force per unit charge, typically volts per meter (V/m). It can be measured using specialized equipment such as an electric field meter.

## 3. What factors affect the strength of an electric field between two points?

The strength of an electric field between two points is influenced by the magnitude and distance of the charges involved, as well as the medium through which the charges are interacting. The type of charge (positive or negative) also plays a role in determining the strength of the electric field.

## 4. How can I approximate an electric field between two points?

To approximate an electric field between two points, you will need to know the distance between the points, the magnitude and type of charge at each point, and the medium through which the charges are interacting. You can then use the formula for electric field strength, which is E = (k * Q) / r^2, where k is the Coulomb's constant, Q is the charge at one point, and r is the distance between the points.

## 5. What is the significance of electric fields in our daily lives?

Electric fields play a crucial role in many aspects of our daily lives, from powering our electronic devices to facilitating communication and transportation. They also play a key role in the functioning of our nervous system and the natural world, such as in the formation of lightning and the behavior of charged particles in Earth's magnetic field.

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