How Do You Calculate Electric Flux Through a Rectangle?

AI Thread Summary
To calculate the electric flux through a rectangle in the xy-plane with an electric field of E=(80.0i + 50k) N/C, first convert the rectangle's dimensions from centimeters to meters, resulting in an area of 0.00162 m². The magnitude of the electric field is approximately 94.34 N/C, but the calculation of electric flux requires vector multiplication, not just multiplying the magnitudes. The initial attempt to find the flux was incorrect due to this misunderstanding. The user was advised to post the question in the homework forum for proper guidance.
arileah
Messages
8
Reaction score
2
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.
 
Physics news on Phys.org
Hello arileah, :welcome:

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, :welcome:

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.
 
This is from Griffiths' Electrodynamics, 3rd edition, page 352. I am trying to calculate the divergence of the Maxwell stress tensor. The tensor is given as ##T_{ij} =\epsilon_0 (E_iE_j-\frac 1 2 \delta_{ij} E^2)+\frac 1 {\mu_0}(B_iB_j-\frac 1 2 \delta_{ij} B^2)##. To make things easier, I just want to focus on the part with the electrical field, i.e. I want to find the divergence of ##E_{ij}=E_iE_j-\frac 1 2 \delta_{ij}E^2##. In matrix form, this tensor should look like this...
Thread 'Applying the Gauss (1835) formula for force between 2 parallel DC currents'
Please can anyone either:- (1) point me to a derivation of the perpendicular force (Fy) between two very long parallel wires carrying steady currents utilising the formula of Gauss for the force F along the line r between 2 charges? Or alternatively (2) point out where I have gone wrong in my method? I am having problems with calculating the direction and magnitude of the force as expected from modern (Biot-Savart-Maxwell-Lorentz) formula. Here is my method and results so far:- This...
Back
Top