# Find the magnitude and the direction of the electric field at the thir

• Richard Ros
In summary, the conversation discusses finding the magnitude and direction of the electric field at the third corner of a triangle with two point charges placed at two corners. The formula F = ((1)/(4πε0))(q1*q2/r^2) is used, and the conversation includes a discussion on converting units correctly. The correct answer is 1.07e+07 N/C at 71.2 degrees above the -x-axis.

## Homework Statement

Two point charges are placed at two of the corners of a triangle as shown in the figure. (Take q1 = -11.3 μC, and q2 = 15.4 μC.) Find the magnitude and the direction of the electric field at the third corner of the triangle. {Correct Answer: 1.07e+07 N/C at 71.2 degrees above the -x-axis}

## Homework Equations

F = ((1)/(4πε0))(q1*q2/r^2)

## The Attempt at a Solution

Attached files. What am i doing wrong? I can't seem to get the correct answer.

#### Attachments

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Last edited:
Did you convert units correctly? Your answers appear to be off by some factors of 10.

Is Ey from q1 positive or negative? [Edited]

Hmm I don't know how I got a negative. But either way when I solve for the magnitude it'll end up being positive. Which unit should I convert? The μc or cm?

Richard Ros said:
Hmm I don't know how I got a negative. But either way when I solve for the magnitude it'll end up being positive.
Yes, but the sign of Ey will affect the answer for the direction angle.
Which unit should I convert? The μc or cm?
Neither μC nor cm is an SI unit.

1 person
Thanks, turns out it was just my conversion.

## What is the formula for finding the magnitude of the electric field?

The magnitude of the electric field is given by the formula E = kQ/r^2, where k is the Coulomb's constant, Q is the charge of the source, and r is the distance from the source to the point where the electric field is being measured.

## How do you determine the direction of the electric field?

The direction of the electric field is always in the direction that a positive test charge would experience a force. For a positive point charge, the electric field lines radiate away from the source. For a negative point charge, the electric field lines point towards the source.

## Can the electric field have a negative magnitude?

Yes, the magnitude of the electric field can be negative. This indicates that the electric field is directed in the opposite direction from what is conventionally defined as the positive direction. The sign of the electric field only indicates the direction, not the strength.

## How does distance affect the magnitude of the electric field?

The magnitude of the electric field is inversely proportional to the square of the distance from the source. This means that as distance increases, the magnitude of the electric field decreases. This relationship is described by the inverse square law.

## What is the unit for measuring the electric field?

The SI unit for electric field is newtons per coulomb (N/C), which is equivalent to volts per meter (V/m). This unit represents the amount of force that a unit positive charge would experience in the presence of an electric field.