Using voltmeters to measure voltage

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To measure the potential difference across parallel resistors, the voltmeter should be connected between points X and W, as X and Y are at the same potential due to a shorting wire, resulting in a 0V reading. Connecting the voltmeter between X and W accurately measures the voltage difference across the parallel resistors. The discussion clarifies that while Y and W are not the recommended option, they would also yield a valid measurement. Understanding the circuit's layout is crucial for correct voltmeter placement. Proper connections ensure accurate voltage readings in parallel resistor configurations.
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Homework Statement


A student needs to connect a voltmeter to measure the potential difference across the parallel
resistors in the circuit shown below
(http://www.bced.gov.bc.ca/exams/search/grade12/english/release/exam/0708PH_p.pdf )
Question 28



Homework Equations


None


The Attempt at a Solution


I thought it would be X and Y, in fact I also think it would be none of them because they don't seem to be in parellel. Can someone please explain why it is X and W?
 
Last edited by a moderator:
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JustinLiang said:

Homework Statement


A student needs to connect a voltmeter to measure the potential difference across the parallel
resistors in the circuit shown below
(http://www.bced.gov.bc.ca/exams/search/grade12/english/release/exam/0708PH_p.pdf )
Question 28



Homework Equations


None


The Attempt at a Solution


I thought it would be X and Y, in fact I also think it would be none of them because they don't seem to be in parellel. Can someone please explain why it is X and W?

Welcome to the PF.

X and Y are at the same potential (voltage) -- there is just a shorting wire between them, so you would read 0V.

If you measure between X and W, you are measuring the voltage difference between the right and left side of the parallel combination of two resistors. Think of all the lines shown as shorting (zero resistance) wires, with no voltage drop along them.
 
Last edited by a moderator:
berkeman said:
Welcome to the PF.

X and Y are at the same potential (voltage) -- there is just a shorting wire between them, so you would read 0V.

If you measure between X and W, you are measuring the voltage difference between the right and left side of the parallel combination of two resistors. Think of all the lines shown as shorting (zero resistance) wires, with no voltage drop along them.

OHHHH ok thanks haha. What about Y and W, even though it is not an option would that work as well?
 
JustinLiang said:
OHHHH ok thanks haha. What about Y and W, even though it is not an option would that work as well?

Yep, Y and W would work as well. Good job!
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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