Which way do I measure the potential difference

In summary, the magnitude of the potential difference between points M and N in a circuit depends on the path chosen and is equal to the battery's voltage regardless of the path. The polarity of the voltages used in the path is determined by the + and - markings on the battery.
  • #1
JessicaHelena
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3

Homework Statement


All the bulbs in the circuits are identical, as are all the batteries. Rank the magnitude of the potential difference between points M and N.
Screen Shot 2018-04-30 at 11.16.52 PM.png


Homework Equations



V=IR

The Attempt at a Solution



My most fundamental question is actually which way do I know to take the potential difference of? For instance, in A, should I only take the potential difference of the batter, or the other way round (where the bulbs are)? In fact, scenario C seems even more ambiguous to me... But once I get the direction of the potential difference right, I think I can tackle the problem.
 

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  • #2
The battery terminals are marked + and -.
 
  • #3
JessicaHelena said:
For instance, in A, should I only take the potential difference of the batter, or the other way round (where the bulbs are)?
The potential difference between any two points in the circuit is the same regardless of the path you choose (exception exists but that's not relevant here).
What does that tell you about VMN in A?
 
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  • #4
@cnh1995 — that it's equal to the battery's voltage? But if it's regardless of the path chosen, I don't quite get C because it seems one way you can get V/2 volts (if V is the battery's voltage) and the other way you can get V + V/2 = 3V/2 volts?

@CWatters — I'm sorry if this should be obvious, but how do the + and - help?
 
  • #5
JessicaHelena said:
the other way you can get V + V/2 = 3V/2 volts?
No, you must get V/2 in this case too. BTW, what is your "other way"?
Check the polarity of the voltages you use in this path (Refer the battery polarity (+ and -)).
 
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  • #6
JessicaHelena said:
@CWatters — I'm sorry if this should be obvious, but how do the + and - help?

Gives you the "direction" of the potential difference. Eg it tells you if M is positive or negative with respect to N.

Perhaps I missunderstand what you mean by "direction".
 
  • #7
JessicaHelena said:
. the other way you can get V + V/2 = 3V/2 volts?

No that other way you get V - V/2 = V/2

Starting at N you go "up" V through the battery then "down" V/2 through the top bulb to get to M.
 

Related to Which way do I measure the potential difference

1. How do I measure potential difference?

To measure potential difference, you will need a voltmeter. Connect the positive (red) probe of the voltmeter to the point where you want to measure the potential difference. Then, connect the negative (black) probe to the reference point, typically the ground. The voltmeter will display the potential difference in volts.

2. Can I measure potential difference using a multimeter?

Yes, a multimeter can also measure potential difference. Set the multimeter to the voltage mode and follow the same steps as using a voltmeter. Make sure to use the appropriate range on the multimeter to get an accurate reading.

3. Which way should I connect the probes to measure potential difference?

The positive probe should always be connected to the point where you want to measure potential difference. The negative probe should be connected to the reference point, typically the ground. This will ensure that you get an accurate reading.

4. What unit is used to measure potential difference?

Potential difference is typically measured in volts (V). However, in some cases, it may be measured in millivolts (mV) or kilovolts (kV).

5. Is potential difference the same as voltage?

Yes, potential difference and voltage are essentially the same. They both refer to the difference in electric potential between two points. However, potential difference is often used in physics and engineering, while voltage is more commonly used in everyday language.

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