Solving Physics+Matlab: Electric & Magnetic Fields

[marko_4454]

For one of my classes I need to implement a model of a charged particle that is giong through electric and magnetic fields.
I can assume these constants:
m=1
q=1
x(0)=0
t-scan: [0 1]
Now the questions:
1)
Simulate the constant acceleration analytic case and plot the result. Add the analytic result from the plot to demostrate the agreement. Assume, E0=[1 0 0] (also E0=E, so constant)
;;My answer: I know that it will be constant because solving for a you get q/m[E+ v' x B] and all of them are constant, but I can't plot it in Matlab, because I have NEVER used it...

2)Solve for E(x)= [5 0 0] B(x)=[0 0 20] v0=[1 1 1]. Plot the position and velocity curves. Observe and measure the ExB drift. (hint: note the vector direction of the drift) and compare it to the expected analytic result--> (which i think its like a sin/cos curve)

Please, I really need to get this done and I have tried it, but I can't get this problem to work...

This is for problem #1

E = [1 0 0]; % define Po
t=0:.5:1; % make a vector L with 100 elements evenly spaced from 0 to 10
B=[1 0 0];
v=[0 0 0];

a2 = E+cross(v,B);

figure;
plot(t,a2);

It doesn't work...and I don't have any idea why...
I have NO idea for Question #2,,,so any help would be greatly appreachiated :)

 

[Cyrus]

because the size of t and a2 do not match.

 

[marko_4454]

and how can I fix it?
acceleration doesn't depend on time so it has to be constant...but how can I put it, so that I say to MATLAB that I want "a" to be a certain value throughout the whole time..
Thanks for you help

 

[LeBrad]

For one of my classes I need to implement a model of a charged particle that is giong through electric and magnetic fields.
I can assume these constants:
m=1
q=1
x(0)=0
t-scan: [0 1]
Now the questions:
1)
Simulate the constant acceleration analytic case and plot the result. Add the analytic result from the plot to demostrate the agreement. Assume, E0=[1 0 0] (also E0=E, so constant)
;;My answer: I know that it will be constant because solving for a you get q/m[E+ v' x B] and all of them are constant, but I can't plot it in Matlab, because I have NEVER used it...

2)Solve for E(x)= [5 0 0] B(x)=[0 0 20] v0=[1 1 1]. Plot the position and velocity curves. Observe and measure the ExB drift. (hint: note the vector direction of the drift) and compare it to the expected analytic result--> (which i think its like a sin/cos curve)

Please, I really need to get this done and I have tried it, but I can't get this problem to work...

This is for problem #1

E = [1 0 0]; % define Po
t=0:.5:1; % make a vector L with 100 elements evenly spaced from 0 to 10
B=[1 0 0];
v=[0 0 0];

a2 = E+cross(v,B);

figure;
plot(t,a2);

It doesn't work...and I don't have any idea why...
I have NO idea for Question #2,,,so any help would be greatly appreachiated :)

For 1, are you trying to plot the magnitude of the acceleration, or a single direction?

You can do figure;plot(t,a2(1)) to see the x-direction acceleration, and similarly figure; plot(t,a2(2)) and figure; plot(t,a2(3)) to see the y and z acceleration components. Or you could do figure; plot(t,norm(a)) to see the magnitude of the acceleration. You are having problems beacuse a2 is just a vector with 3 components, so when you say plot(t,a2) it tries to put one of the a2 components with each t value, which won't work unless t is the same size, and even then it won't give you what you want.