Voltage/Battery Terminal confusion

  • Thread starter XPTPCREWX
  • Start date
  • Tags
    Confusion
In summary: If you have two batteries connected in series, there is still going to be a potential difference because the source of energy is shared between the two batteries.
  • #1
XPTPCREWX
101
0
1.) Why can't you measure the potential difference across two batteries terminals, let's say a positive terminal from battery A and a negative terminal from battery B?
Theoredically there is still a potential difference...therefore voltage...right?
 
Engineering news on Phys.org
  • #2
You can... unless you are talking about two independent batteries (not wired together). If that is the case, then you have an incomplete circuit, thus no current flow.
 
  • #3
XPTPCREWX said:
1.) Why can't you measure the potential difference across two batteries terminals, let's say a positive terminal from battery A and a negative terminal from battery B?

Because they are not connected as a circuit.

XPTPCREWX said:
Theoredically there is still a potential difference...therefore voltage...right?

No there wouldn't be. From an Ohm's Law point of view, since they are not connected as a circuit, no current can flow and no potential difference will exist.

CS
 
  • #4
So there needs to be current induced by the voltage you are measuring?

I was under the impression that EVERYTHING had electrical potential/voltage.
Now this leads me to believe that a Voltmeter will NOT in fact read voltage, but moreover voltage drop?
 
  • #5
It simply depends on the input impedance of the voltmeter. REAL WORLD voltmeters do not have infinite impedance so they require a current to flow in order to work.
 
  • #6
XPTPCREWX said:
I was under the impression that EVERYTHING had electrical potential/voltage.
Now this leads me to believe that a Voltmeter will NOT in fact read voltage, but moreover voltage drop?
They measure voltage DIFFERENCE. It's meaningless to say something has a voltage without saying what it has a voltage relative to.
For batteries it is relative to the other terminal so your meter has to connect between the two terminals to measure the voltage between them.
 
  • #7
I understand all of this, but I was asking from more of a scientific view point...
Although I think this answers my question PERFECTLY well.

Averagesupernova said:
It simply depends on the input impedance of the voltmeter. REAL WORLD voltmeters do not have infinite impedance so they require a current to flow in order to work.

To sum it up, its just that our typical modern day conventional Voltmeters cannot measure Voltage alone, but rather a "voltage drop" (the difference across a conductor) in reference to a circuit but dependent of the current induced in it... Or as supernova suggested Impedence.
 
  • #8
If you want a voltmeter that takes no current (direct current, not alternating) once it's charged, then the electrostatic voltmeter is your friend.

Don't expect to measure much below a kV or so though.
 
  • #9
The two batteries' terminals can have completely different voltages, measured with reference to some third object. For example, you could charge up one 9V battery's metal case with a Van de Graff (static electricity) generator so that its negative terminal was at 1000V with respect to the Earth. The battery's chemical potential will then cause its positive terminal to always be 9V greater than its negative. The positive terminal will therefore be at 1009V, with respect to the Earth.

The issue arises with voltmeters, which, as has been said, are not perfect, and do not have infinite impedance. As soon as you connect the voltmeter to the two batteries, a very small current will flow, equalizing the charge on the batteries until the meter reads zero. This happens in the blink of an eye for any normal voltages, and appears to not happen at all.

The issue of voltage being only a relative quantity is extremely important, but entirely separate from this mechanism.

- Warren
 
Last edited:
  • #10
XPTPCREWX said:
1.) Why can't you measure the potential difference across two batteries terminals, let's say a positive terminal from battery A and a negative terminal from battery B?
Theoredically there is still a potential difference...therefore voltage...right?


Here is a site where u can purchase terminals online and this is a 100% trusted site for purchasing the terminals and connectors online just go through this link and grab the things that u need and this site offers some discounts in the bulk purchasing of the products. here is the site http://terminalscheap.com/
 
  • #11
Two batteries - or two lumps of metal, for that matter, can be at different potentials. A meter with a high enough input resistance can measure this but the act of measurement is likely to bring their two potentials together because some finite current will flow through the measuring device.
The thing about a battery is that it has a source of energy which will keep the potential difference across its terminals even when you measure it or take current inot a load.
 

1. What is the difference between voltage and battery terminal?

Voltage refers to the electrical potential difference between two points in a circuit, whereas battery terminal refers to the physical connection points on a battery where electrical energy is drawn from. Voltage is measured in volts (V) and battery terminals are typically labeled as positive (+) and negative (-) to indicate the direction of current flow.

2. Why is it important to understand the difference between voltage and battery terminal?

Understanding the difference between voltage and battery terminal is important because it affects how electrical circuits and devices function. For example, connecting a battery to a circuit with the wrong polarity (positive to negative and vice versa) can cause damage to the circuit or device.

3. Can a battery with a higher voltage be used in place of a battery with a lower voltage?

No, a battery with a higher voltage should not be used in place of a battery with a lower voltage. This is because the higher voltage battery may supply more energy than the circuit or device can handle, causing damage. It is important to use batteries with the correct voltage for the specific application.

4. How can I determine the voltage of a battery?

The voltage of a battery can typically be found on the label or packaging of the battery. It can also be measured using a multimeter, a tool commonly used by scientists and engineers to measure electrical properties such as voltage, current, and resistance.

5. What is the purpose of battery terminals?

Battery terminals serve as the connection points between the battery and the circuit or device it is powering. They provide a path for the flow of electrical energy from the battery to the circuit or device, allowing it to function. The positive terminal is typically connected to the positive end of the battery, which has a higher voltage, while the negative terminal is connected to the negative end, which has a lower voltage.

Similar threads

Asking some Capacitor questions to help my understanding
    • Electrical Engineering
Replies
19
Views
1K
What could be draining the car battery and how can it be fixed?
    • Electrical Engineering
Replies
8
Views
863
Earth grounded, where does the current flow?
    • Electrical Engineering
Replies
19
Views
3K
Are the terminals of a Battery neutral?
    • Electrical Engineering
Replies
27
Views
4K
How do I properly connect a bench power supply to a pulse generator for testing?
    • Electrical Engineering
Replies
19
Views
1K
Pn junction under forward bias
    • Electrical Engineering
Replies
14
Views
2K
I An attempt to understand the associated variable conventions in circuits
    • Electromagnetism
Replies
1
Views
822
Why is source force + electrostatic force = 0 inside battery?
    • Introductory Physics Homework Help
Replies
10
Views
176
Safe to charge a Lithium Battery with a Voltage Limit?
    • Electrical Engineering
Replies
2
Views
1K
Connect parallel batteries with wrong poles
    • Electrical Engineering
Replies
17
Views
1K

Hot Threads

Recent Insights

Back
Top