# Field and force with three charges

• Squall
In summary, the conversation discusses the calculation of the electric field at the location of Q1, due to Q2. The diagram and positions of the charges are given, and the conversation refers to using Coulomb's Law. After some confusion about the units of position, it is determined that the electric field calculation is incorrect due to a conversion error.
Squall

## Homework Statement

At a particular moment, three small charged balls, one negative and two positive,are located as shown in the figure. q1 = 3 nC, q2 = 7 nC, and q3 = -5 nC.

What is the electric field at the location of Q1, due to Q2?

y
q1
|
|
|
q2______q3____x

Okay that is the given diagram the if q2 is at (0,0) then q1 is at (0,4); q3 at (3,0);
and the distances are in centimeters

## Homework Equations

I'm using Coulomb's Law which states that E = 9e9*(q/r^2)r-hat

## The Attempt at a Solution

So I thought all I have to do is plug in the values

[9e9*(7e-9/(.004)^2)]*<0,4,0> = <0,3937500,0>N/C

please help me, I've been staring at this for a while and I cannot figure out why I don't get the right answer, I shouldn't have to consider the other charges because they don't affect the field created by q2 just the net field, so why is this not correct I have no idea.

Thanks Again for all the help guys

In what units are the components of the position?

ehild

The components of the positions are in centimeters. (cm)

If so, 4 cm = 0.04 m. And you have to use the unit vector in the direction of <0,4,0>.

ehild

Oh yes your right, I just kept converting the cm to m wrong, putting an extra zero in front of it like they were mm or something. Thank You so much it really helps having someone else look at this. I knew I had to be making some stupid mistake.

## 1. What is the formula for calculating the electric field of three charges?

The formula for calculating the electric field of three charges is given by E = k(Q1/r1^2 + Q2/r2^2 + Q3/r3^2), where k is the Coulomb's constant, Q1, Q2, and Q3 are the charges, and r1, r2, and r3 are the distances between the charges and the point where the electric field is being calculated.

## 2. How do the direction and magnitude of the force change when the distances between the charges are altered?

When the distances between the charges are altered, the direction and magnitude of the force also change. The force between two charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them. So, as the distance between the charges increases, the force decreases and vice versa.

## 3. What is the principle of superposition in the context of three charges?

The principle of superposition states that the total electric field at a point due to multiple charges is equal to the vector sum of the individual electric fields at that point. In the case of three charges, the electric field is the sum of the electric fields produced by each individual charge.

## 4. How does the presence of a third charge affect the electric field between two other charges?

The presence of a third charge can alter the electric field between two other charges. This is because the third charge can create an additional electric field that adds to or subtracts from the electric field between the first two charges, depending on the direction and magnitude of the third charge.

## 5. What are some real-life applications of the concept of three charges and electric fields?

The concept of three charges and electric fields has several real-life applications, such as in electronics and technology, where it is used to design and understand the behavior of circuits and devices. It is also used in medical imaging techniques like magnetic resonance imaging (MRI) and positron emission tomography (PET) to create images of the human body. Additionally, this concept is essential in understanding and predicting the behavior of lightning and other natural phenomena.

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