Just a quick check on a mistake

[DominikAntonioSajko]

This task was given in auditory excercises of "measurements in ee" course.
A sliding resistor of 50 kΩ is used in the potentiometer connection to adjust the voltage on the voltmeter to 60 V, with a characteristic resistance of 1 kΩ/V. If the ends of the potentiometer are connected to a 120 V voltage source and its slide is placed exactly in the middle, how much will the voltmeter show?

The part that is boxed in red color is where I think I found a mistake so I want to check it with you.
Shouldn't the "Ruk" ("Rtotal") really be R1+R2||Rv ?

 

[AnalogKid]

Correct. BUT -

its slide is placed exactly in the middle,

so R1 = R2.

ak

 

[rjenkinsgb]

Without knowing the specific voltage range selected on the voltmeter, the question is unanswerable.

eg. The 1K Ohms per volt is the full scale value; if it were eg. set to 100V range, the meter resistance would be 100K regardless of the voltage actually being measured.

The assumption is a 60V range, but nowhere is that stated, apparently?

 

[AnalogKid]

Thought about bringing up that, decided not to complicate things. Given the entry-level nature of the question, my guess is that it does not deal with that level of specificity.

ak

 

[crutschow]

my guess is that it does not deal with that level of specificity.

But you need the meter range to determine the meter resistance and calculate the voltage.

 

[DominikAntonioSajko]

Shouldn't the "Ruk" ("Rtotal") really be R1+R2||Rv ?

Guessing everything else is done correctly, does the highlighted equation seem to be valid?

 

[DominikAntonioSajko]

But you need the meter range to determine the meter resistance and calculate the voltage.

I suppose meter range is 60 V.

 

[Pommie]

Assuming meter range is 60V then the calculations look correct.

Did I miss something here? Is this a right answer but wrong method so zero marks type question?

Mike.

 

[AnalogKid]

But you need the meter range to determine the meter resistance and calculate the voltage.

Completely agree. But my read of the (poorly worded) question is that the correct answer either is an equation with Rv as a variable, or a single value based on an implied value for Rv. Of those two options, Rv = 60 K seems appropriate for this level.

ak