# Coulombs Law find the magnitude and direction ?

• airforce840
In summary: Do you have a TI-84 Plus? If so, you can use the Physics Toolbox that comes with it to do the calculations.
airforce840
We are dealing with Coulombs law or w/e in Physics right now AND I DONT GET IT lol In my homework. it gives numbers like +6.0 (weird u symbol)C and i jus don't understand how to find the magnitude and direction of everything..

Patrick

Well, do you have a sample problem you have trouble understanding with... If so post it.

ok... here's a sample prob. actually its the one I am on..

1. Three point charges, q1, q2, and q3, lie along the x-axis at x=0, x=3.0 cm, and x= 5.0 cm, respectively. Calculate the magnitude and direction of the electric force on each of the three point charges when q1= +6.0 mu symbol C, q2=+1.5 muC and q3= -2.0 muC.

This all deals with "the superposition principle" and yea..this is hard stuff considering we were just working with lens...and i hated them and wish we were back to them already lol.

patrick

The "weird u symbol" you speak of means micro, which is 1 * 10^-6. So $$6 \mu C$$ is the same thing as $$6 \cdot 10^{-6} C$$. Remember that the equation for force between two charges is $$F=\frac{kq_{1}q_{2}}{r^{2}}$$

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ok, calm down. This isn't really that hard, it's just in a new format. I assume that you've done gravity? $$F=\frac{G m_{1} m_{2}} {r^2}$$? Well coulomb's law is basically the same. Instead of G you have k, and instead of masses you have charges. So for the force between two charges, you just put q1 as one charge (say q1=+6.0 muC) and q2 as the other charge (say 1.5muC) and the r is the distance between them (say 3.0cm). so you just plug those numbers into the equation and you've got the force between those two charges. If say q2=-2.0muC then the force would be negative (the negative charge q2 times the positive charge q1).

Now superposition is really not that difficult either. Basically, if you have three charges, q1, q2, and q3, the TOTAL force on q1 is the force on q1 by q2 PLUS the force on q1 by q3. And there you go. You've got the force. Just a small hint: Don't forget the directions of the force. If one of the force is negative, take that into account. If you have three charges and your looking for the force on the one in the middle, don't forget which way each force is going. You'll understand the hint better once you do the problem.

$$F = k\frac{q_1q_2}{r^2}$$

When the magnitude of the force is positive (negative-negative or positive-positive) then it is a push force, pointing away from the other charge.
When the magnitude of the force is negative (negative-positive) then it is a pull force, pointing to the other charge.
Also you will usually see charges in micro-Coulombs: $$\mu C$$, which is a milionth of a Coulomb. The SI unit C is usually considered too large for normal static charges, which are just a few $$\mu C$$ or $$nC$$ (nano-Coulombs, or bilionth of a Coulomb).

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Thanks 4 the Help

I got to class and had some more explanation... i wish in class they would be as blunt and understandable though... only thing i still have a problem with is like.. trying to find the vectors part..the directions.. like

q1 q2

q3 q4 i don't understand after finding the Forces acting on them..like the directions...which comes out as a Degree.. its jus...confusing i guess..i don't know how to explain in on here lol. easier by mic.

but thanks for the help.. anyone have calculator programs for physics? i have a ti -84 plus...

patrick

## What is Coulomb's Law?

Coulomb's Law is a fundamental law of physics that describes the electrostatic interaction between two charged particles. It states that the force between two charged particles is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.

## How do you calculate the magnitude of the force using Coulomb's Law?

The magnitude of the force between two charged particles can be calculated using the formula F = (k * q1 * q2) / r^2, where F is the force, k is the Coulomb's constant (8.99 x 10^9 Nm^2/C^2), q1 and q2 are the charges of the particles, and r is the distance between them.

## What is the direction of the force calculated using Coulomb's Law?

The direction of the force is along the line connecting the two charged particles and is either attractive or repulsive, depending on the sign of the charges. If the charges are of opposite signs, the force is attractive, and if the charges are of the same sign, the force is repulsive.

## Can Coulomb's Law be used for both positive and negative charges?

Yes, Coulomb's Law can be used for both positive and negative charges. The sign of the charges is taken into account in the formula, and it affects the direction of the force.

## How is Coulomb's Law related to Newton's Law of Gravitation?

Coulomb's Law and Newton's Law of Gravitation are both inverse-square laws that describe the force between two objects. However, Coulomb's Law deals with electric charges, while Newton's Law of Gravitation deals with the force of gravity between masses.

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