Estimate the electric flux through the sphere

• -EquinoX-
In summary, the question asks to estimate the electric flux through an imaginary spherical surface of radius R, with a point charge Q placed a distance 2R above its center. According to Gauss law, the net electric flux through a closed surface surrounding no charge is zero. However, in this case, the charge is outside the closed surface, so the total flux out of the sphere is indeed zero. To find the flux from Q that passes through the sphere, the total flux emitted by Q must be considered. This can be found by calculating the portion of the expanding sphere's area intercepted by the sphere. While there may be some minor inaccuracy, it should not affect the final answer.
-EquinoX-

Homework Statement

A point charge Q is placed a distance 2R above the center of an imaginary spherical
surface of radius R. Estimate the electric flux through the sphere

The Attempt at a Solution

I think the answer is 0 as Gauss law states that the net electric flux through a closed surface that surrounds no charge is zero. In this case the charge is outside the closed surface (sphere). Am I right?

The total flux out of the sphere is zero all right. But I think you are supposed to find the flux from Q that passes through the sphere. Some goes in the top and then goes out the bottom, to give that total of zero.

Find the total flux emitted by the Q. What portion of that is intercepted by the sphere? Think of the expanding sphere at the head of those flux arrows as they pass through the center of the sphere of radius R. The cross sectional area of the sphere will be some fraction of the area of that expanding sphere. A couple of area calcs will find you the answer. I see a little inaccuracy but I don't think it is a problem.

So the answer is not 0?

1. What is electric flux?

Electric flux is a measure of the electric field passing through a given surface. It is defined as the product of the magnitude of the electric field and the area of the surface it passes through, multiplied by the cosine of the angle between the electric field and the surface normal.

2. How do you calculate electric flux through a sphere?

To calculate the electric flux through a sphere, you need to know the electric field passing through it. Then, you multiply the electric field by the surface area of the sphere and by the cosine of the angle between the electric field and the surface normal. This will give you the total electric flux passing through the sphere.

3. Why is electric flux important?

Electric flux is important because it helps us understand the strength of an electric field passing through a given surface. It is also useful in determining the net charge enclosed within a closed surface, known as Gauss's Law.

4. What factors affect the electric flux through a sphere?

The electric flux through a sphere is affected by the strength and direction of the electric field passing through it, as well as the size and shape of the sphere. The angle between the electric field and the surface normal also plays a role in determining the electric flux.

5. Can the electric flux through a sphere be negative?

Yes, the electric flux through a sphere can be negative. This occurs when the electric field and the surface normal are in opposite directions, resulting in a negative value for the electric flux. It is important to pay attention to the direction of the electric field when calculating electric flux.

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