Problem Solver has with simple equation
11-16-2022, 06:09 PM (This post was last modified: 11-17-2022 02:30 PM by Nick1941.)
Post: #1
 Nick1941 Junior Member Posts: 8 Joined: Jun 2022
Problem Solver has with simple equation
There is an equation in chemistry that relates the energy of an electron in an orbital with quantum number n in a hydrogen atom. The equation is E_n = E_n1/(n^2) with E_n1 = -2.18E-18. When I compute this on the Home screen with, say, n=4, it immediately displays the result: -1.3625E-19. However, when I enter that equation in the solver, and in the numbers screen have -2.18E-18 in the En1 field and 4 in the n field, and move to the En field and select Solve, the calculator battery symbol changes to an hourglass like it's crunching through a very complex calculation. After a few minutes, I just aborted the calculation. Why does the Solver app have such a problem with such a simple equation?

Additional information: The Solver seems to have problems with negative exponents greater than or equal 10. If I set X = 2.2E-9 and n = 4 and set up the equation Y = X/(n^2), when I click Solve, it immediately solves the problem. However, if I set X = 2.2E-10 and run the same equation, the Solver gets locked up in an hourglass situation and can't solve the problem in a reasonable amount of time. BTW, I have found the same problem using the Virtual Calculator.
11-18-2022, 03:08 PM
Post: #2
 Arno K Senior Member Posts: 470 Joined: Mar 2015
RE: Problem Solver has with simple equation
I can't reproduce your problem, my both Primes solve your 2nd task in no time, Y=1.375E-11, both use newest firmware (2021 11 25) and so it must have to do with your settings. I even tried n and N in the solver-app.
Arno
11-18-2022, 04:47 PM
Post: #3
 Nick1941 Junior Member Posts: 8 Joined: Jun 2022
RE: Problem Solver has with simple equation
Very strange! BTW, my version number is 2.1.14603 (2021 12 02) which seems to be a later version that (2021 11 25). Maybe they broke something in the newer version. For number format, I have tried Standard, Fixed, Scientific, Engineering, and Floating. For entry, I have tried Textbook, Algebraic, and RPN. The problem always remains.
11-18-2022, 05:42 PM
Post: #4
 roadrunner Senior Member Posts: 448 Joined: Jun 2015
RE: Problem Solver has with simple equation
I can reproduce the error with the emulator version 2021 06 09 and on the handheld version 2021 12 02.
11-18-2022, 06:13 PM
Post: #5
 Nick1941 Junior Member Posts: 8 Joined: Jun 2022
RE: Problem Solver has with simple equation
Thank you, Roadrunner.
Those are the versions I have of both items.
Glad to see someone else could reproduce the problem.
11-23-2022, 07:16 PM
Post: #6
 Nick1941 Junior Member Posts: 8 Joined: Jun 2022
RE: Problem Solver has with simple equation
One way around this problem is to define a function to perform the operation instead of using the Solver. For example, I created the function ElectronEnergy as -2.18E-18/n^2 with n as the input variable. Running ElectronEnergy(4) correctly and immediately produces the answer:
-1.3625E-19. Of course, to replace the Solver equation En = -2.18E-18/n^2, one would have to create two functions: one that computes En with n as the input (shown above) and the other that computes n with En as the input, such as a function called QuantumLevel as SQRT(-2.1E-18/En) with En as the input variable.
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