Using voltmeters to measure voltage

[JustinLiang]

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?

 

[berkeman]

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.

 

[JustinLiang]

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?

 

[berkeman]

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!

 

[rwisz]

I can provide an explanation for why it is necessary to use the voltmeter to measure the potential difference across the parallel resistors in the given circuit.

Firstly, it is important to understand that voltage is a measure of the potential difference between two points in a circuit. In this case, the student needs to measure the potential difference across the parallel resistors, which will provide information about the amount of electrical energy being transferred through the circuit.

Using a voltmeter is the most accurate and precise way to measure voltage in a circuit. Voltmeters are specifically designed to measure the potential difference between two points and are calibrated to provide accurate readings. Other instruments, such as ammeters, are designed to measure current and would not be suitable for measuring voltage.

Furthermore, in a parallel circuit, the current splits into different branches, with each branch having its own resistance. This means that the potential difference across each resistor may be different, and therefore, cannot be measured by simply adding the voltages measured across each individual resistor. Using a voltmeter allows the student to directly measure the potential difference across the parallel resistors, taking into account the different branches and their respective resistances.

In conclusion, using a voltmeter is necessary to accurately measure the potential difference across the parallel resistors in the given circuit. It is the most suitable instrument for this purpose and will provide the most accurate and precise measurement.