29 votes
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How do batteries lose capacity in winter?

It is true that battery performance is reduced at colder temperatures. This is because temperature has an effect on chemical processes within the batteries, especially lithium-ion batteries, used most ...
joseph h's user avatar
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25 votes
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Does current run forever in water? (assuming the supply voltage is there forever)

It is energetically unfavourable to split a water molecule into the two ions $\text{H}^+$ and $\text{OH}^-$ i.e. you need to put in energy to do it. However at room temperature water molecules have a ...
John Rennie's user avatar
24 votes

Can we call rusting of iron a combustion reaction?

Rusting of iron is an oxidation reaction, but not combustion. Although the reaction's equation looks the same as the equations for combustion (e.g., of hydrogen and oxygen mixture, $2H_2+O_2=2H_2O$), ...
Roger V.'s user avatar
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21 votes

How do batteries lose capacity in winter?

A deeper, physics/chemistry approach to the question: A battery (whatever chemistry it uses) invariably contains solid electrodes and liquid electrolyte (there are batteries that have it the other way ...
fraxinus's user avatar
  • 7,906
10 votes

Does current run forever in water? (assuming the supply voltage is there forever)

The ions are converted into gases $H_2$ and $O_2$ at the electrodes, so water is gradually being removed from the container - but it requires a very very large amount of charge to flow in order to ...
sammy gerbil's user avatar
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9 votes

In a circuit, does a battery create electrons which it 'injects' into the copper wire?

Are electrons created from a battery and then 'injected' into the copper wire? If no, then does that mean that the battery looses power because the copper wire has run out of free electrons? Sort of -...
pjc50's user avatar
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9 votes
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Is the reason why a normal battery ran out of "juice" that it has reached electrostatic equilibrium between its two terminals?

The movement of charges, that is the current, when the circuit is closed is due to electrochemical reactions taking place at the anode and cathode. Very simply put, the first reaction is an oxidation ...
Gert's user avatar
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9 votes

How do batteries lose capacity in winter?

In addition to the charge in the battery itself, you also need to consider increased HVAC usage. Unlike an internal combustion engine vehicle, which produces waste heat as a byproduct of combustion ...
StalePhish's user avatar
7 votes

Does current run forever in water? (assuming the supply voltage is there forever)

Fist of all, saying that there is one hydrogen ion for $10^6$ ions of water is wrong.ph is the negative of log of concentration of hydrogen ions. pH 6 means that there is $10^{-6}$ moles of hydrogen ...
Rishabh Jain's user avatar
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7 votes
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Confusion in definition of emf

Electromotive force is the electrical work done to move a unit positive charge from the positive electrode to the negative electrode. It is not about moving the charge through the whole circuit. It is ...
Thirsty for concepts's user avatar
6 votes

In a circuit, does a battery create electrons which it 'injects' into the copper wire?

A battery is a combination of cells. Cells work by converting chemical energy, commonly known as Gibbs Free Energy, to electrical energy. Inside a cell, a redox reaction takes place that maintains a ...
Soumyadwip Chanda's user avatar
6 votes

In a new unconnected battery, has a chemical reaction already occurred to cause excess electrons on anode end?

Both reactions have taken place, but involving only an extremely limited number of electrons. At the cathode electrons have been captured from the cathode assembly, including the metal terminal. But ...
Philip Wood's user avatar
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6 votes
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How does cold make batteries drain faster yet simultaneously they should be refrigerated to keep a charge?

I have always known via common knowledge that batteries drain quicker when it's cold... Yes, because lowering the ambient temperature causes chemical reactions to proceed more slowly, so a battery ...
Bob D's user avatar
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6 votes
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Why does the potential across the terminals of battery increase on moving from negative terminal to positive terminal?

This is dealt with in the field of electrochemistry. Here is a simplified explanation: Chemical reactions involve the outermost electrons of the reactant atoms and some of those reactions can be ...
niels nielsen's user avatar
6 votes
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How batteries create voltage?

Voltage (up to a factor) is the work one electron can produce when travelling from anode ($-$) to cathode ($+$). Current is the number of electrons flowing. The energy needed to do the work comes from ...
Vasily Mitch's user avatar
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5 votes
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At an atomic level, what happens when you connect two batteries in series so that their voltages are added?

Chemistry and Physics of Batteries in Series What happens at the atomic level inside a cell when putting two batteries in series? Short Answer: Characteristics of a single cell vs. two cells in ...
Thomas Lee Abshier ND's user avatar
5 votes
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How can a battery 'come back to life'?

In general, any electrochemical reaction in a battery creates concentration gradients of different compounds between electrodes, which tend to form thin layers of different substances near them. Some ...
kkm -still wary of SE promises's user avatar
5 votes

Confusion in definition of emf

The statement of Kirchhoff's second law closest to what you've quoted is Around any closed loop the algebraic sum of the potential differences is zero. $$\sum \Delta V=0$$ This could be re-worded as ...
Philip Wood's user avatar
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5 votes

How do batteries lose capacity in winter?

The charge in a rechargeable battery is literally a charge, i.e. a quantity of electrons that have been moved. Charge is conserved; temperature change does not alter it. It is normal to stop adding ...
Whit3rd's user avatar
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4 votes

How is potential difference maintained in a battery?

So technically, in those physics examples the voltage isn't fixed in those batteries. The potential drops, just very slowly for small currents. For example, if the voltage is 12V and some small ...
Ben S's user avatar
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4 votes
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breakdown voltage in vacuum

When you get near perfect vacuum, the surface condition of your electrodes becomes the dominant factor in determining the breakdown. Any asperities on the cathode will become field emitters. If there ...
Floris's user avatar
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4 votes

Why do liquid metals conduct electric current?

Even in liquid metals, the current is mostly carried by electrons, ions are just too heavy in comparison to play a major role in conduction (though the situation is different in polar liquids). The ...
KF Gauss's user avatar
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4 votes

What makes fruits conduct electricity?

Most fruits and vegetables will conduct electricity because they contain water (with extra ions). To generate electricity you need to stick two metal electrodes into the fruit. The metals have to be ...
Philip Wood's user avatar
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4 votes

Why does the Anode and not the Cathode corode during eletrolysis of water into $H_2$ and $O_2$?

Metals tend to be oxidized, not reduced. Oxidation happens at the anode (positive charged one during electrolysis, it wants electrons), thus the cathode is protected look into cathodic protection. ...
ChemEng's user avatar
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4 votes

At an atomic level, what happens when you connect two batteries in series so that their voltages are added?

One way to think of this is as follows: for your two-battery system with the batteries in series, the positive terminal of battery "A" doesn't know or care what voltage the negative terminal of ...
niels nielsen's user avatar
4 votes

At an atomic level, what happens when you connect two batteries in series so that their voltages are added?

I think that your analogy of "surplus" of electrons is wrong in one sense, and incomplete in another sense. First, what do you consider a "normal" and a "surplus" of electrons? Second, if you have a "...
ESL's user avatar
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4 votes
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Why are(n’t) rechargeable batteries damaged by partial charging?

The answer is more about chemistry than physics - but then there are those who will claim that chemistry is just applied physics. There's also a bit of electronics in the mix - which is also a form of ...
Floris's user avatar
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4 votes
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Nernst Equation and Energy

You take the meaning of the half cell potential E wrong. It does not mean if you put through the half cell $\rm{1 C}$, you store $\rm{1 J}$. Additionally, you ignore the half cell potential change ...
Poutnik's user avatar
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