basic voltage query

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WBahn

Joined Mar 31, 2012
26,398
Where is this "300" coming from?

Where is this "25" coming from?

What are the units on the 300? What are the units on the 12? What are the units on the 25? If you would bother to put some units on there, I bet you would find that your "0.04" does not have the units you think it does and, at that point, you would know that your work was incorrect.

You better stop being so sloppy with your work. If you don't, then you are wasting your time and money studying in this field. You are effectively pulling numbers out of thin air with absolutely no basis for what you are doing. You are basically a random number generator.
 

WBahn

Joined Mar 31, 2012
26,398
bit of both

I'm as good as my teachers that teach me as they say
I think I see part of your problem. It is either: (a) you have a high degree of arrogance and believe that you know more than the teachers, when you demonstrably don't understand stuff that is covered the first day in most Circuits I courses, or (b) you truly do have absolute idiots for teachers. I don't know which it is, possibly some combination of both. But in either case you are going to have serious difficulties moving forward. In the latter case you are completely wasting your time studying under people that are clueless about the field. This would be like paying some school to learn how to become a gourmet chef but the school has hired teachers who have never cooked anything in their life. In the former case you will continue to refuse to take the advice and instruction you are given because you are convinced you know better.
 

WBahn

Joined Mar 31, 2012
26,398
300 total R
I'm using v I r and changing this formula.
so 200 +100 for voltmeter
v I r is not a formula.

v = i * r is a formula.

What you are doing is grabbing any formula you can find and throwing whatever numbers you find at it without bothering to consider if it is the right formula to use or whether the numbers you are using make sense to use in it. You don't seem to have any desire to understand the fundamental concepts.

Even assuming that 300 kΩ was a meaningful value for this problem (which it is not), why are you dividing 300 kΩ by 12 V? What about this "formula" leads you to do that?

And then why do you multiply it by 25?
 

Thread Starter

Albert Symes

Joined Oct 22, 2015
41
your right.i'll give up

and now i'll carry on

so battery voltage /total restistance x r1 = voltage

12/300,000 =0.00004

0.00004 x r1(100,000 ohm)= 4v

I understand v=ir I understand that,if you look at my replies ive even been able to manipulate that formula.i just haven't spelled it out
 

Thread Starter

Albert Symes

Joined Oct 22, 2015
41
I'm just looking for the answer.

nobody has been able to give me that.

joe jester may be the best teacher on here,i don't know,wbahn,has some knowledge

who is the best teacher is it the one with a degree,a masters,a cert,the one without all,i cant say?
 

dl324

Joined Mar 30, 2015
12,677
so battery voltage /total restistance x r1 = voltage

12/300,000 =0.00004

0.00004 x r1(100,000 ohm)= 4v

I understand v=ir I understand that,if you look at my replies ive even been able to manipulate that formula.i just haven't spelled it out
But the meter resistance isn't in series with the other two resistors. What you drew was correct.

You don't need to use Ohm's Law to calculate the voltage the meter will measure.

What is the voltage at the node between the two resistors? Without using Ohm's Law...
 

dl324

Joined Mar 30, 2015
12,677
An unfortunate side effect of you not understanding the circuit and the values involved has allowed you to arrive at the correct answer using the wrong circuit. Maybe the values were chosen so you could calculate the result in your head; which is what I did.

Change the two resistors to 50K and redo the exercise.
 
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