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Question on FrankHertz Experiment :/

  1. Nov 5, 2013 #1
    Sorry to deviate from the template but I think that a simple explanation will be useful here. In our lab we just did the frank hertz experiment, and we used two methods to find the excitation energy for mercury.

    The first is that we manually adjusted the voltage and manually recorded peaks from the currents. Then we used a least squares fitting for a Voltage Vs Peak number graph. They said from the slope of the graph, we are capable of getting a measurement for the excitation energy. In which I got ≈5V

    so Energy = 5eV which I think is a fairly close number from what I have read on the internet.

    The second method had asked us to plot a graph using data collected electronically. The graph is shown in the attachment. From this we were supposed to take the difference in voltages from the Highest Peak and Lowest peak and divide by the number of intervals. However From this I get a really small value, nowhere near the proper value. This leads me to believe that either A) the settings on the computerized grapher were not set up correctly or B) I am not understanding something correctly.

    I am hoping someone can help me perhaps identify if I am missing something with the computerized data.

    P.S The y-axis is current and the x-axis should be voltage on the graph. Sorry it is not in the image :(
     

    Attached Files:

  2. jcsd
  3. Nov 5, 2013 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    x is certainly not the voltage in V, this should be obvious if you look at the graph (and know that the real value is somewhere around 5V). This looks like an excel diagram. Do you have the voltage somewhere in the data source?
     
  4. Nov 5, 2013 #3
    When we did the experiment the data that collected on the computer showed up as Potential 1 and Potential 2. So I thought that perhaps that the 2nd set of data was just supposed to be labeled as current instead of potential 2. I can try to give you the data although I don't know how much use it will be :/ The left column is "Potential 1" the second is "Potential 2"

    0.076 -0.032
    0.081 -0.032
    0.081 -0.027
    0.081 -0.037
    0.09 -0.037
    0.1 -0.027
    0.1 -0.027
    0.105 -0.037
    0.11 -0.032
    0.115 -0.027
    0.125 -0.032
    0.12 -0.032
    0.129 -0.037
    0.139 -0.037
    0.149 -0.027
    0.149 -0.022
    0.159 -0.022
    0.149 -0.027
    0.149 -0.017
    0.159 -0.017
    0.173 -0.012
    0.183 -0.002
    0.193 -0.007
    0.188 -0.002
    0.188 -0.002
    0.208 0.002
    0.217 0.002
    0.217 -0.002
    0.242 0.017
    0.256 0.051
    0.252 0.066
    0.261 0.066
    0.261 0.076
    0.261 0.076
    0.266 0.09
    0.261 0.11
    0.271 0.115
    0.281 0.125
    0.291 0.139
    0.305 0.178
    0.32 0.188
    0.335 0.222
    0.359 0.252
    0.374 0.281
    0.383 0.315
    0.388 0.335
    0.383 0.339
    0.379 0.359
    0.393 0.379
    0.403 0.388
    0.418 0.398
    0.427 0.393
    0.437 0.408
    0.437 0.422
    0.442 0.422
    0.457 0.442
    0.457 0.466
    0.457 0.481
    0.471 0.486
    0.481 0.501
    0.496 0.53
    0.505 0.579
    0.51 0.647
    0.525 0.716
    0.54 0.803
    0.554 0.901
    0.559 0.984
    0.564 1.043
    0.569 1.092
    0.579 1.131
    0.593 1.179
    0.603 1.204
    0.608 1.204
    0.623 1.184
    0.637 1.155
    0.647 1.126
    0.652 1.087
    0.662 1.062
    0.662 1.033
    0.681 1.004
    0.691 0.999
    0.701 1.013
    0.711 1.023
    0.716 1.048
    0.73 1.092
    0.735 1.16
    0.74 1.243
    0.74 1.321
    0.755 1.424
    0.779 1.595
    0.789 1.8
    0.794 1.995
    0.794 2.156
    0.808 2.308
    0.828 2.43
    0.833 2.518
    0.833 2.567
    0.852 2.586
    0.872 2.537
    0.886 2.435
    0.911 2.298
    0.916 2.161
    0.921 2.015
    0.935 1.897
    0.935 1.81
    0.96 1.766
    0.974 1.79
    0.979 1.868
    0.994 1.995
    1.009 2.181
    1.013 2.41
    1.009 2.611
    1.033 2.86
    1.053 3.231
    1.067 3.558
    1.082 3.792
    1.087 3.949
    1.101 3.998
    1.111 3.993
    1.111 3.954
    1.131 3.866
    1.145 3.656
    1.16 3.397
    1.184 3.123
    1.194 2.864
    1.199 2.669
    1.204 2.542
    1.214 2.449
    1.223 2.449
    1.238 2.571
    1.258 2.777
    1.267 3.074
    1.287 3.441
    1.297 3.861
    1.297 4.217
    1.302 4.481
    1.321 4.725
    1.336 4.974
    1.346 5.121
    1.355 5.15
    1.365 5.121
    1.375 5.043
    1.375 4.965
    1.375 4.882
    1.385 4.735
    1.399 4.501
    1.409 4.227
    1.419 3.934
    1.429 3.636
    1.438 3.363
    1.443 3.128
    1.453 2.943
    1.453 2.816
    1.453 2.718
    1.458 2.65
    1.463 2.62
    1.468 2.611
    1.477 2.63
    1.487 2.713
    1.487 2.806
    1.492 2.894
    1.492 2.977
    1.502 3.094
    1.512 3.241
    1.512 3.436
    1.521 3.651
    1.531 3.875
    1.531 4.095
    1.541 4.325
    1.541 4.515
    1.541 4.657
    1.546 4.799
    1.556 4.984
    1.565 5.165
    1.57 5.321
    1.58 5.477
    1.59 5.648
    1.6 5.805
    1.604 5.907
    1.609 5.961
    1.629 5.946
    1.639 5.829
    1.643 5.697
    1.648 5.565
    1.658 5.409
    1.663 5.17
    1.683 4.838
    1.692 4.476
    1.697 4.134
    1.712 3.812
    1.741 3.578
    1.746 3.509
    1.751 3.529
    1.756 3.592
    1.761 3.675
    1.77 3.832
    1.785 4.071
    1.795 4.408
    1.81 4.769
    1.824 5.17
    1.834 5.614
    1.844 6.005
    1.853 6.274
    1.863 6.469
    1.868 6.62
    1.878 6.718
    1.878 6.762
    1.883 6.781
    1.883 6.781
    1.883 6.781
    1.893 6.747
    1.902 6.669
    1.907 6.532
    1.912 6.381
    1.917 6.23
    1.917 6.103
    1.922 5.946
    1.937 5.726
    1.946 5.399
    1.956 5.048
    1.966 4.711
    1.966 4.427
    1.971 4.178
    1.985 3.978
    1.99 3.841
    1.99 3.753
    1.995 3.709
    2.005 3.719
    2.015 3.812
    2.02 3.983
    2.024 4.149
    2.034 4.325
    2.049 4.574
    2.049 4.847
    2.054 5.082
    2.078 5.365
    2.088 5.853
    2.098 6.249
    2.103 6.527
    2.107 6.694
    2.107 6.796
    2.107 6.85
    2.103 6.899
    2.103 6.923
    2.107 6.928
    2.107 6.967
    2.117 7.001
    2.122 7.031
    2.122 7.065
    2.127 7.099
    2.127 7.133
    2.122 7.153
    2.137 7.172
    2.127 7.172
    2.137 7.182
    2.137 7.177
    2.142 7.167
    2.147 7.162
    2.142 7.162
    2.147 7.158
    2.147 7.158
    2.151 7.133
    2.161 7.104
    2.161 7.06
    2.166 7.026
    2.166 6.972
    2.171 6.923
    2.171 6.884
    2.166 6.835
    2.166 6.811
    2.176 6.777
    2.181 6.703
    2.186 6.596
    2.195 6.425
    2.195 6.225
    2.205 6.015
    2.21 5.766
    2.215 5.531
    2.225 5.258
    2.249 4.926
    2.254 4.647
    2.264 4.476
    2.264 4.383
    2.274 4.349
    2.283 4.432
    2.293 4.642
    2.308 4.93
    2.317 5.287
    2.332 5.687
    2.337 6.005
    2.347 6.332
    2.352 6.645
    2.357 6.864
    2.366 7.026
    2.376 7.197
    2.381 7.353
    2.386 7.514
    2.396 7.621
    2.405 7.68
    2.405 7.724
    2.415 7.753
    2.415 7.758
    2.415 7.758
    2.42 7.753
    2.42 7.739
    2.43 7.7
    2.435 7.636
    2.44 7.543
    2.444 7.441
    2.444 7.338
    2.449 7.265
    2.449 7.201
    2.454 7.114
    2.469 6.913
    2.493 6.659
    2.479 6.347
    2.493 6.01
    2.503 5.731
    2.503 5.516
    2.523 5.326
    2.532 5.219
    2.542 5.204
    2.552 5.263
    2.552 5.385
    2.557 5.541
    2.562 5.678
    2.567 5.829
    2.581 6.112
    2.591 6.454
    2.606 6.767
    2.611 7.05
    2.625 7.319
    2.63 7.553
    2.63 7.714
    2.635 7.807
    2.65 7.924
    2.654 8.037
    2.664 8.12
    2.664 8.188
    2.674 8.212
    2.689 8.188
    2.694 8.154
    2.694 8.11
    2.703 8.032
    2.713 7.919
    2.723 7.748
    2.733 7.519
    2.742 7.27
    2.752 7.016
    2.762 6.728
    2.772 6.459
    2.772 6.239
    2.791 6.054
    2.806 5.971
    2.825 6.029
    2.84 6.23
    2.845 6.488
    2.85 6.737
    2.86 6.923
    2.869 7.109
    2.879 7.368
    2.894 7.685
    2.899 7.954
    2.913 8.198
    2.928 8.413
    2.938 8.559
    2.947 8.652
    2.967 8.691
    2.991 8.642
    3.006 8.476
    3.021 8.237
    3.031 7.963
    3.045 7.685
    3.045 7.441
    3.055 7.265
    3.065 7.114
    3.079 7.016
    3.084 7.001
    3.099 7.026
    3.114 7.167
    3.118 7.411
    3.128 7.67
    3.133 7.88
    3.143 8.081
    3.148 8.252
    3.158 8.422
    3.162 8.603
    3.172 8.764
    3.177 8.872
    3.182 8.95
    3.187 9.023
    3.197 9.077
    3.197 9.121
    3.197 9.155
    3.201 9.175
    3.211 9.228
    3.211 9.267
    3.221 9.282
    3.216 9.297
    3.216 9.292
    3.221 9.292
    3.216 9.282
    3.216 9.282
    3.211 9.248
    3.216 9.263
    3.221 9.263
    3.221 9.258
    3.216 9.253
    3.221 9.248
    3.221 9.238
    3.221 9.233
    3.221 9.223
    3.216 9.223
    3.221 9.214
    3.216 9.204
    3.221 9.194
    3.216 9.189
    3.221 9.175
    3.221 9.165
    3.216 9.16
    3.216 9.15
    3.221 9.136
    3.216 9.136
     
  5. Nov 5, 2013 #4
    The second set of data to me looks like currents because it peaks, drops down, goes up, down etc...
     
  6. Nov 5, 2013 #5
    AH! I have figured out my problem. What we did was measure the accelerating potential from 0-60ish volts. Now if you scale the measurements on the x axis by a factor of 20, you get a voltage roughly in that range. Once you take the difference between the voltage representative of the last peak and the first peak and divide it by 10. You get a voltage of about 5 :) Hurray haha. I think this figured it out, but if there are any other suggestions let me know!
     
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