# How Do You Calculate Electric Flux Through a Rectangle?

• arileah
In summary, electric flux is a measure of the amount of electric field lines passing through a given surface. It is calculated by taking the dot product of the electric field vector and the surface area vector, and its unit is volts per meter squared (V/m^2). This is different from electric field, which measures the force experienced by a charge at a specific point in space. Gauss's Law relates to calculating electric flux by stating that it is equal to the charge enclosed by a closed surface divided by the permittivity of free space. This is useful for calculating electric flux in situations with high symmetry.
arileah
Hello,

The problem:

A 3.60cm x 4.50cm rectangle lies in the xy-plane. What is the electric flux through the rectangle if E=(80.0i + 50k) N/C ?

My attempt:

First convert the rectangle units from cm to m.

4.50cm = 0.045m
3.60cm = 0.036m

Find the area of the rectangle.

A = 0.036m x 0.045m = 0.00162 m^2

Find the magnitude of the electric field.

E = sqrt (50^2 + 80^2) = 94.34 N?C (aprox.)

Multiply the two,

electric flux = E * A = 0.15283 Nm^2 / C (aprox.)

However, this answer is wrong. Could anyone point me in the right direction? Thank you.

Hello arileah,

This looks like homework and should be posted in the homework forum -- there's a mandatory template there.
Your error is at the point where you multiply the two: that is a vector multiplication, not a magnitude multiplication.

BvU said:
Hello arileah,

This looks like homework and should be posted in the homework forum -- there's a mandatory template there.
Your error is at the point where you multiply the two: that is a vector multiplication, not a magnitude multiplication.

Thank you! I am new to using physics forums. I'll post it to the homework forum.

## 1. What is electric flux?

Electric flux is a measure of the amount of electric field lines passing through a given surface.

## 2. How is electric flux calculated?

Electric flux is calculated by taking the dot product of the electric field vector and the surface area vector.

## 3. What is the unit of electric flux?

The unit of electric flux is volts per meter squared (V/m^2).

## 4. What is the difference between electric flux and electric field?

Electric flux is a measure of the electric field passing through a surface, while electric field is a measure of the force experienced by a charge at a specific point in space.

## 5. How is Gauss's Law related to calculating electric flux?

Gauss's Law states that the electric flux through a closed surface is equal to the charge enclosed by that surface divided by the permittivity of free space. This can be used to calculate electric flux in situations with high symmetry.

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