# Physics 2 Lab

**Topics:**Electric charge, Electromagnetism, Electric field

**Pages:**4 (631 words)

**Published:**September 23, 2012

Lab 201: Electric Field by Point Charges

Section: 121A-H02

Date: February 8, 2012

Objective:

To compute electric field and corresponding field lines caused by point charges using MATLAB.

Theoretical Background:

-electrons are negative, protons are positive

-magnitude of force between A and B is:

, is 8.98755E9.

-electric field is the region around a charged object

-strength of electric field:

=

-electric field lines are used to visually show the field

Procedure:

Our procedure for this lab was very simple. We had to determine a correct MATLAB code to write. We inputted a code into MATLAB and received figure 1.1, the pot of the electric filed of a positive point charge. Our next goal was to plot the graph of the x position of a test charge in the presence of two positive charges versus the total electric filed at that point, we ended up with figure 1.2. We then repeated this plot, but with a positive and negative charge (figure 1.3). Lastly, we proceeded to plot the electric filed with two positive charges using a vector field plot (figure 1.4); and it was repeated for a positively and negatively charged particle in order to receive figure 1.5.

Results:

Figure 1.1

Figure 1.2

Figure 1.3

Figure 1.4

Figure 1.5

Part II

Procedure:

This was just copying code directly from the lab manual and seeing the results of the electric fields for various charged particles.

Data:

Part One Code:

clear all

esp0 = 8.85e-12;

k = 1/(4*pi*esp0);

q1 = 1e-9; %First Charge

q2 = -1e-9; %Second Charge

a = 1;

x = -2.1:0.1:2.1;

E1 = q1*k*(x+a)./abs(x+a).^3;

E2 = q2*k*(x-a)./abs(x-a).^3;

Etotal = E1 + E2;

plot(x, Etotal)

xlabel 'x'; ylabel 'Etotal';

grid on

title 'Total Electric field vs. x';

Part One Graph

Part Two Code:

[x, y] = meshgrid(-2.1:0.2:2.1, -2.1:0.2:2.1);

r1S = (x).^2 + (y-a).^2;

r1 = sqrt(r1S);

r2S = (x).^2 + (y+a).^2;

r2 = sqrt(r2S);

e1x = (x)./r1;

e1y = (y-a)./r1;

e2x = (x)./r2;

e2y...

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