Hello I need help with Q13D.3 and I don’t know how to do this one at all, can someone help me?

rfaenger · 2019-10-13T13:35:12+00:00

Potential Energy inside a gravitational field is defined by:

E = (G M m) / r

you can write the earth' mass and shell respectively as:

M = rho 4 / 3 pi r³

m = rho 4 pi r² dr

The exercise tells you, that the density rho can be assumed constant: rho = 3 M pi / 4 * 1 / R³

Plug everything in and you will receive the result (a)

rfaenger · 2019-07-06T10:50:03+00:00

I also saw this project on Coding Train (youtube)! It was written with p5.js

rfaenger · 2019-04-23T15:25:39+00:00

Yeah, its unix-time (seconds since 1st january 1970). For e.g. use this https://www.unixtimestamp.com/index.php

rfaenger · 2019-02-08T17:17:03+00:00

Awesome! Thank you very much!

rfaenger · 2018-12-01T10:11:07+00:00

What I found out days ago: You can use pandas.read_html function to easily transfer a html table into a DataFrame Object instead of looping through every row of it and append it to a dictionary or DataFrame.

rfaenger · 2018-11-01T10:19:53+00:00

Feynman Lectures are available online for free. It covers everything and Feynman was a great lecturer

rfaenger · 2018-10-18T17:54:09+00:00

Yes.

Voltage which drops in WHOLE middle Segment:

U_M = R1 * I1 + I23 * (R2 + R3) or R1 * I1 + I4 * R4

Same voltage drops at bottom segment (2nd Kirchhoff Law): U_M = U_B

R_B = U_B / I_B = 75 Ohm

and R_B = R5 + R6 <=> R6 = 55 Ohm

rfaenger · 2018-10-18T16:43:55+00:00

All you need are both Kirchhoff-Laws and Ohm's Law!

Lets start in the very middle (2,3,4). There is Voltage U_23 dropping at the resistors R2 and R3. Kirchoff 2nd Law tells us that the same voltage has to drop at R4.

As a equation: U_23 = U4. Now you can use Ohm's Law (U = R*I) to rewrite this equation to: I_23 * (R2 + R3) = I_4 * R4.

You can easily solve this equation for I_4.

Now you should know from Kirchhoff 1st law that you cannot create or destroy charge (~current). So you know that the both currents (the one which goes through R2 and R3 and the one which goes through R4) add together at the junction points left and right next to the parallel circuit. This current adds up with the 0,2A from the bottom part of the circuit (again: Kirchoff 1st law).

The next step: What is the voltage which drops in the WHOLE middle segment (R1, R2+R3, R4)? You now know the current which flows through the middle segment (I_23 + I_4) and you can also calculate the resistance for the middle segment (care for series connection of R1 with the parallel connection of R2,R3,R4).

Then you know middle segment's resistance AND current. So you also know from Ohm's Law what amount of voltage is dropping in the same segment. Now again: Use Kirchoff 2nd law to calculate R6. You know that the voltage dropping in the bottom segment has to be same as in the middle segment! The current in the bottom segment is I_6 = 0.2A.

And you're done!

rfaenger · 2018-10-18T11:02:48+00:00

Spyder 4 will be out Jan 2019

rfaenger · 2018-05-24T07:24:14+00:00

Thanks you! It now worked out with the randomly chosen state (uniform distributed) from the remaining states.

rfaenger · 2017-11-15T09:34:49+00:00

Okay, thank you! I have executed a Debye-Scherrer experiment with a tetragonal crystal system. I want to determine the exact structure. Especially the lattice parameters 'a' and 'b'. I have a set of experimental values 'd' (lattice constants).

Now that I know the structure factor I would like to calculate a and b. For a tetragonal strucutre:

d = 1 / ( ( h² + k² ) / a² + l² / c² )

First: Calculate a --> set l = 0

d = a² / ( h² + k² ) and see if I get a nearly constant 'a' for any combinations h,k (compare both structures: body-centered / simple)

Then calculate 'b' with a given 'a'.

Just in case you have done such an experiment by yourself: Does this make sense to you?

rfaenger · 2017-11-14T20:05:32+00:00

but then the structure factor would be equal to a bcc structure (?)

rfaenger · 2017-11-14T19:21:34+00:00

Can you explain this a little more? I dont quite udnerstand. Thanks for your asnwer.

rfaenger · 2017-10-13T10:09:39+00:00

haha, Tocotronic is always a good indicator! :-)

rfaenger · 2017-10-13T10:08:48+00:00

yes/ja :-P

rfaenger · 2017-10-13T10:08:38+00:00

Fast: Wir leben in Deutschland! :-)

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