# Voltage in a series circuit

• B
If I had a simple series circuit with only a single resistor, and I used a voltmeter to find the voltage between a point at the end of the circuit and another point, which was moved from the beginning to the end of the circuit, what would I find at these various point?

Would the voltage remain the same as the points got closer, or would it change?

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DennisN
2020 Award
Hi FS98,
Question 1: What do you think yourself?
Question 2: Is there a power supply (i.e. a voltage source) connected to the circuit or not?

• FS98
anorlunda
Staff Emeritus
I need a schematic diagram to understand what you're asking.

• FS98
Hi FS98,
Question 1: What do you think yourself?
Question 2: Is there a power supply (i.e. a voltage source) connected to the circuit or not?
Yes there’s a power supply. Here’s a picture of something like what I’m thinking of.

My intuition from having used a voltmeter before is that it would be the same everywhere. Although of my intuition is correct, I’m left a bit confused.

A flowing body of water on an incline is often used to explain voltage, resistant and current. If we take the difference in potential energy per unit mass between the bottom of that body of water and a point at the beginning of the flowing water, and then move that point closer and closer to the point at the bottom of the incline, I would think that the potential energy per unit mass would decrease. It seems like this would also apply to voltage down the wire of a circuit.

So that’s why I’m asking. My intuition is telling me different than what seems to make sense.

#### Attachments

anorlunda
Staff Emeritus
If you put the voltmeter leads at points 1 and 2, it will show zero volts if the wire is idea with zero resistance.

If the wire has nonzero resistance, there will be a slight voltage V12. it would get smaller as you bring the two leads closer to each other. However, the slight voltage may be only a few microvolts, too small for you to measure with an inexpensive meter. Your picture shows the voltage of the battery and the ohms of the resistor, but it does not specify how thick the wires are. The thinner the wires, the more resistance they have.

In circuit analysis, we typically assume that all wires have zero resistance even if that is not strictly true.

• FS98
DennisN
2020 Award
Yes there’s a power supply. Here’s a picture of something like what I’m thinking of.
It's good you posted a picture. I have two more questions:
What do you think your voltage meter will show when you measure between...
1. ...point 1 and 2 in your picture?
2. ...point 2 and 3 in your picture?

EDIT: anorlunda has already answered question 1. • FS98
It's good you posted a picture. I have two more questions:
What do you think your voltage meter will show when you measure between...
1. ...point 1 and 2 in your picture?
2. ...point 2 and 3 in your picture?

EDIT: anorlunda has already answered question 1. I want to say that it will measure 9v for question 2.

My intuition along with the responses make me think that voltage is only found between resistive parts of a circuit.

• davenn
DennisN
2020 Award
I want to say that it will measure 9v for question 2.
Correct.

Now we have just got two more questions left:
What do you think your voltage meter will show when you measure between...
3. ...point 3 and 4 ?
4. ...point 4 and 1 ?

• FS98
Correct.

Now we have just got two more questions left:
What do you think your voltage meter will show when you measure between...
3. ...point 3 and 4 ?
4. ...point 4 and 1 ?
I believe 0 for question 3 and 9v for question 4.

• davenn
DennisN
2020 Award
I believe 0 for question 3 and 9v for question 4.
Correct!

• FS98