Constant Current in Batteries? How?

In summary, the essential anatomy of a battery is a cathode and an anode separated by an electrolyte, and the anode absorbs electrons. When the battery is connected to a wire, the current is a function of the resistive load in the circuit and can vary depending on the resistive nature of the other parts of the circuit. The current also changes from moment to moment as the circuit operates. Additionally, Ohm's Law states that current is directly proportional to voltage, and vice versa. This means that as current increases, voltage also increases, and as current decreases, voltage decreases.
  • #1
plazprestige
33
0
I do not know the exact electrochemical reactions which make a battery work, but I understand that the essential anatomy of a battery is a cathode and an anode separated by an electrolyte, and the anode absorbs electrons. When the battery is connected to a wire, the electrons move from the anode tot he cathode, producing a current.

I have two questions.

Due to the electrical potential difference, it would follow reason that the electrons would accelerate toward the cathode when a wire is connected. If this is the case, then how is there a constant current in the battery if current is defined by dq/dt (change in charge over time)?

Secondly, what is the difference between two batteries of different voltage? How is the electrical potential difference lowered or increased? (more of an engineering question)

Thanks in advance for responses. I am new to to these forums and hope to learn as well as contribute.
 
Physics news on Phys.org
  • #2
Constant current batteries are not produced in primary cells, such as lead-acid, NiCd, Alkaline, NiMH, etc., because constant voltage works better. Cells are constructed to produce constant voltage. As load current is demanded, the voltage drops due to internal resistance. By minimizing resistance, better voltage stability is obtained.

Nuclear cells are still being developed. These cells work better in the constant current mode. The voltage changes as the load varies but the current reamains approximately constant. Any battery bought for commercial use is the constant voltage type.
 
Last edited:
  • #3
So the current in a wire connected to a standard 12 V battery is not constant?
 
  • #4
plazprestige said:
So the current in a wire connected to a standard 12 V battery is not constant?

The current in a wire connected to a standard battery is a function of the resistive load to which the battery is applied.

If you mean JUST a wire then you have a short circuit and all bets are off (except for the fact that you are likely to get a VERY hot wire and/or battery)
 
  • #5
I guess I'm not being very clear, as the response does not answer my question. I am not asking about the engineering of the battery itself which allows it to function (except for my second question on how batteries increase voltage), but rather how the basic principles which allow batteries to work are leading me to believe something which does not occur.
 
  • #6
plazprestige said:
Due to the electrical potential difference, it would follow reason that the electrons would accelerate toward the cathode when a wire is connected.

No. Crudely speaking, the atoms in the wire get in the way, so there is a terminal velocity. It's not like a cathode-ray tube in which the electrons travel through vacuum.
 
  • #7
An electric wire has millions-trillions of electrons. Therefore, the process never ends up. Electrons keep flowing and flowing till there is a potential difference.
 
  • #8
physics kiddy said:
An electric wire has millions-trillions of electrons. Therefore, the process never ends up. Electrons keep flowing and flowing till there is a potential difference.

Seems to me you have cause and effect backwards here. Electrons don't flow "until there is a potential difference", they flow BECAUSE there is a potential difference.
 
  • #9
phinds said:
Seems to me you have cause and effect backwards here. Electrons don't flow "until there is a potential difference", they flow BECAUSE there is a potential difference.

Actually it's not a cause and effect thing, but rather, a chicken and egg thing. In order to create a PD (potential difference) charges must move and separate. Then when that happens, other charges can be influenced by the associated electric field due to charge separation and move as result.

Is PD "caused" by charge motion, or is charge motion "caused" by PD? Actually it's both. The problem with thinking that charges move because of PD lies with the flow inside the battery. The charges inside are literally moving AGAINST the electric field, i.e. "uphill". Hence these charges are not moving BEACAUSE of PD, but rather their motion gives rise to the PD. The charges outside the battery are going "downhill", and they move due to E field influence or PD.

Claude
 
  • #10
cabraham said:
Actually it's not a cause and effect thing, but rather, a chicken and egg thing. In order to create a PD (potential difference) charges must move and separate. Then when that happens, other charges can be influenced by the associated electric field due to charge separation and move as result.

Is PD "caused" by charge motion, or is charge motion "caused" by PD? Actually it's both. The problem with thinking that charges move because of PD lies with the flow inside the battery. The charges inside are literally moving AGAINST the electric field, i.e. "uphill". Hence these charges are not moving BEACAUSE of PD, but rather their motion gives rise to the PD. The charges outside the battery are going "downhill", and they move due to E field influence or PD.

Claude

That's a good explanation and certainly seems right for a battery. thanks.
 
  • #11
phinds said:
The current in a wire connected to a standard battery is a function of the resistive load to which the battery is applied.


And the current in a given wire does not just change overall depending on the resistive nature of the rest of the things in the circuit, it also changes from moment to moment as the other parts of the circuit operate. For instance, a bulb slowly heats up after being turned on, and becomes more resistive in the process, thereby drawing less current from the battery through the wire.
 
  • #12
I know that current is directly proportional to voltage but how is voltage directly proportional to current ?
 
  • #13
physics kiddy said:
I know that current is directly proportional to voltage but how is voltage directly proportional to current ?

HUH ? Do you know Ohms Law?
 
  • #14
Our teacher said so when he was describing Ohm's Law. I agree that current is directly proportional to voltage but how is the reverse possible.
 
  • #15
Well let me ask you the question in math. If A is proportional to B, it B proportional to A?
 
  • #16
Yes, it is...
 
  • #17
phinds said:
Well let me ask you the question in math. If A is proportional to B, it B proportional to A?

Then what's your problem?
 

1. What is constant current in batteries?

Constant current in batteries is a steady flow of electric current that is maintained at a constant level over a period of time. This is typically achieved through the use of a regulating device, such as a resistor, that limits the flow of current to a specific value.

2. Why is constant current important in batteries?

Constant current is important in batteries because it helps to ensure a consistent and reliable power supply. It also helps to prevent overcharging or over-discharging of the battery, which can damage the battery and reduce its lifespan.

3. How is constant current achieved in batteries?

Constant current can be achieved through the use of a regulating device, such as a resistor or a specialized circuit, that controls the flow of current in the battery. Some batteries also have built-in mechanisms, such as a chip or a control board, that help to maintain a constant current.

4. Can constant current be adjusted in batteries?

Yes, constant current can be adjusted in batteries through the use of different regulating devices or by changing the settings on a built-in control mechanism. The specific method for adjusting the constant current will depend on the type and design of the battery.

5. What are the benefits of using constant current in batteries?

Using constant current in batteries can help to prolong the lifespan of the battery by preventing overcharging or over-discharging. It also helps to maintain a stable and reliable power supply, which is important for devices that require a consistent level of power to function properly.

Similar threads

I How a Battery creates a Potential difference in an electrical current
    • Electromagnetism
Replies
14
Views
3K
I Can current flow in an open circuit?
    • Electromagnetism
Replies
4
Views
1K
I How is Potential Difference Created across a Resistor?
    • Electromagnetism
Replies
4
Views
1K
Electrical potential energy questions for a battery circuit
    • Electromagnetism
Replies
4
Views
862
B How is surface charge accumulated?
    • Electromagnetism
2
Replies
36
Views
3K
I An attempt to understand the associated variable conventions in circuits
    • Electromagnetism
Replies
1
Views
822
Question about battery -- Looking into the electrode effects on the battery
    • Chemistry
Replies
4
Views
1K
I Is the Poynting Vector Field the Only Factor in Energy Flow in Circuits?
    • Electromagnetism
Replies
14
Views
1K
Current Flow Through a Common Part of a Circuit (batteries and light bulbs)
    • Electromagnetism
Replies
18
Views
3K
I Electric potential and potential difference
    • Electromagnetism
Replies
7
Views
1K

Hot Threads

Recent Insights

Back
Top