People. sorry it's me one more time with the possibility that the Professor did a mistake (I know I know, its probably my mistake, but I need your help to show me where i did wrong.)

In the exercise I needed to find the current passing through the Resistor 2 (and 1 as well, but If i find one then i automatically find the other)
The Professor showed the calculations only partially, not all the way through the end
The found value for Ir2 is 3Amps
but according to my calculations I got 4.5 Amps

show me please where I'm wrong (and please pardon me my possible math mistakes)
I know i often do obvious mistakes. but this time just can't find it

(Ib is like 8 Amps as well.)

 

I found my mistake already. Shame on me. Sorry guys I really tried to find it before. (for more than 2 hours)
so much time lost.
I think I should visit a psychologist, for problems with focusing

 

Glad you found it, because it's hard for us to work the problem since you didn't tell us what the value of the voltage source was.

 

Hi,

The voltage source is presumably 10 volts

However, i'd like to see the answer that was obtained by 'jean'.

 

I found my mistake already. Shame on me. Sorry guys I really tried to find it before. (for more than 2 hours)
so much time lost.
I think I should visit a psychologist, for problems with focusing

This was a learning opportunity. Sometimes just writing the question down to explain it to someone else can help get past a mental block and reach the answer. This works more often than you might think. So when you're stuck, slow down and write it out. Whether you ask for help or not, that process alone can help.

 

Hi,

The voltage source is presumably 10 volts

However, i'd like to see the answer that was obtained by 'jean'.

But how do you know it was 10 V?

You reverse engineered that from the work given. But the claim by the person that presented the work was that there was a mistake in it. How do you know that the mistake wasn't using 10 V instead of the value that was given in the problem?

 

But how do you know it was 10 V?

You reverse engineered that from the work given. But the claim by the person that presented the work was that there was a mistake in it. How do you know that the mistake wasn't using 10 V instead of the value that was given in the problem?

Hello there,

A wise detective once said, "Many things are possible but not all things are reasonable".

It is reasonable to assume it was 10v, or else that would have required a very stupid mistake. Yes, it's very possible it's not, but then that was noted as a presumption. It wont stand the test of falsification if it really isnt 10v, but in the mean time it's not a bad guess. I posed it as a guess.
What you are doing is posing a guess as well, that it may not be 10v. So i am guessing that it is 10v, you are guessing that it is not.
In cases where we have to guess there is a heuristic:
https://en.wikipedia.org/wiki/Occam's_razor

However, you can probably prove this one way or the other, but before you quote me on that too, that's a guess at this point also as i did not do it yet either. You can go over his original equations and see if he did something ELSE wrong, like in the math itself. That would raise the chance that it was really 10v, but if he did not make a mistake in the math then that would raise the chance that he made a different mistake, which could very well have been that 10v was really something else. I just didnt feel like taking it that far as i happen to be in the middle of a bunch of other stuff too at this point in time. Note that there are a ton of other mistakes possible too, which we cant know yet.
Also note that i mentioned that it would be nice to see his/her actual final result.

Whenever i use a heuristic of any kind i realize that i may have to go back and recalculate something or do something over again, but if the heuristic ends up winning the game, i assume it is correct, at least up until the next test of that assumption. I wont assume the heuristic is perfect though, except maybe after thousands of tests, and even then it is good to leave the door open for some unusual problem that comes up that could never have been foreseen.

 

Hello there,

A wise detective once said, "Many things are possible but not all things are reasonable".

It is reasonable to assume it was 10v, or else that would have required a very stupid mistake.

You completely missed the point. I told the TS that they didn't tell us the value of the voltage source. The point is that, when giving a problem, the information needed to solve the problem should be clearly given. They should not require that the people they are asking for free help from (or anyone else, for that matter, such as a grader, a customer, or a supervisor) have to play detective and ferret out the basic information hidden in the details of their work.

 

You completely missed the point. I told the TS that they didn't tell us the value of the voltage source. The point is that, when giving a problem, the information needed to solve the problem should be clearly given. They should not require that the people they are asking for free help from (or anyone else, for that matter, such as a grader, a customer, or a supervisor) have to play detective and ferret out the basic information hidden in the details of their work.

Hi,

Sure, but in the mean time i took a guess. We're still waiting for a direct answer also, but why not make a big deal out of it because someone took a guess. Maybe i should have modified that quote, "All things are possible, but some are unreasonable".