# Electric flux

#### TYUTNTT

Hello sir
How to solve this an electric charge of 8.85*10^-13 C is placed at the center of a sphere of radius 1m. The electric flux through the sphere is:
1. 0.2NC ^-1 m²
2. 0.1NC ^-1 m²
3. 0.3NC ^-1 m²
4. 0.01NC ^-1 m²

#### topsquark

Forum Staff
First, this is not a Mecanics question. I am moving the thread to the "Electricity and Magnetism" Forum.

Hint: What is the equation for electric flux?

-Dan

#### TYUTNTT

Φ = E A cos(θ)

Φ = 8.85*10^-13C*3.14*1m²=27.789Cm²*10^-13

#### topsquark

Forum Staff
Φ = E A cos(θ)

Φ = 8.85*10^-13C*3.14*1m²=27.789Cm²*10^-13
That isn't correct. If you are going to use that form then you need to integrate over the angle $$\displaystyle \theta$$ as it covers the whole surface of the sphere.

The flux through a sphere with a single point charge encolsed in a sphere is
$$\displaystyle \Phi _E = \dfrac{q}{ \epsilon _0 }$$

I can show you this using Gauss' Law but it doesn't seem to me that you know Calculus.

-Dan

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