Potential difference of an emf with internal resistance

AI Thread Summary
When charging a battery with an emf of 2V and internal resistance of 0.1 ohm at 5 amperes, the current flows from the negative terminal to the positive terminal inside the battery, reversing the usual discharge direction. The potential difference across the battery terminals is calculated using the formula V = E - ir, yielding 1.5V, but the actual potential difference during charging is 2.5V. The confusion arises from the terms "anode" and "cathode," which change based on the battery's operating mode; during charging, the positive terminal is the anode. Understanding conventional current flow is essential, as it moves from the positive terminal through the external circuit and returns to the negative terminal. Clarifying these concepts helps resolve the initial misunderstanding regarding current direction and potential difference.
Tanishq Nandan
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Homework Statement


A battery of emf 2V and internal resistance 0.1ohm is being charged with a current of 5 ampere.
In what direction will the current flow inside the battery?What is the potential difference between the two terminals of the battery?

Homework Equations


If a battery of emf E and an internal resistance r has a current i flowing through it,potential difference across it's terminals,say V is defined as:
V=E-ir

The Attempt at a Solution


When we connect a battery in a circuit,INSIDE THE BATTERY,current flows from the negative terminal to the positive terminal,which discharges the battery(correct me if I'm wrong here please)
So,while recharging,the direction should be reversed,shouldn't it?
Also,the formula stated above,yields the answer to be 1.5V
But,the answer given is:
Current flows from the anode to the cathode
V.d=2.5 Volts
I am guessing if I just get the reasoning for the first part,the formula stated could be modifed to yield the correct answer,but why does the current inside the battery flow from the negative terminal to the positive terminal,wouldn't that discharge the battery?
 
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Tanishq Nandan said:
When we connect a battery in a circuit,INSIDE THE BATTERY,current flows from the negative terminal to the positive terminal,which discharges the battery(correct me if I'm wrong here please)
Conventional current (movement of positive charges) flows from the positive terminal, though the external circuit, and back to the negative terminal of the battery. Internal to the battery, conventional current is "pumped" from its negative terminal to its positive terminal. When analyzing circuits it's in your best interests to express things in terms of conventional current as that is the accepted standard and less likely to cause confusion amongst those reading your equations and explanations.
So,while recharging,the direction should be reversed,shouldn't it?
Correct.
Also,the formula stated above,yields the answer to be 1.5V
But,the answer given is:
Current flows from the anode to the cathode
V.d=2.5 Volts
I am guessing if I just get the reasoning for the first part,the formula stated could be modifed to yield the correct answer,but why does the current inside the battery flow from the negative terminal to the positive terminal,wouldn't that discharge the battery?
You don't need to modify the formula, just get the current direction correct. That means assigning the appropriate sign to the current value to reflect its direction with respect to the direction assumed for the current definition in place when the formula in question was written.
 
gneill said:
Internal to the battery, conventional current is "pumped" from its negative terminals to its positive terminal
Ok,I got that.
Now,if I am correct and the direction does get reversed,doesn't that mean that conventional current is moving from the positive to the negative terminal now?
But,as I stated in the post,the answer given is:current flows from anode to cathode.
 
Tanishq Nandan said:
Ok,I got that.
Now,if I am correct and the direction does get reversed,doesn't that mean that conventional current is moving from the positive to the negative terminal now?
But,as I stated in the post,the answer given is:current flows from anode to cathode.
The terms "anode" and "cathode" can sometimes be tricky to interpret when a device is not being used in its normal operating mode. For a battery that is driving current into a circuit the positive terminal is designated as the cathode. If the battery is being charged and current is thus flowing into its positive terminal, that terminal is then referred to as the anode.

Take a look at the Wikipedia article:
https://en.wikipedia.org/wiki/Anode
 
gneill said:
The terms "anode" and "cathode" can sometimes be tricky to interpret when a device is not being used in its normal operating mode. For a battery that is driving current into a circuit the positive terminal is designated as the cathode. If the battery is being charged and current is thus flowing into its positive terminal, that terminal is then referred to as the anode.

Take a look at the Wikipedia article:
https://en.wikipedia.org/wiki/Anode

Ok,got it.Crystal clear now,thanks!
 
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