# Tag Info

18

Yes, the total mass of a battery increases when the battery is charged and decreases when it is discharged. The difference boils to Einstein's $E=mc^2$ that follows from his special theory of relativity. Energy is equivalent to mass and $c^2$, the squared speed of light, is the conversion factor. I would omit the scenario I. If the lithium is leaking from ...

11

Heat. Batteries have internal resistance and so produced heat when current flows through them (Joule heating). Also, the heat generated increases by the square of that current. E.g, doubling the charging current causes the heat produced to be increased 4 times. Ultracapacitors are a different technology that can be used like batteries--they have very very ...

10

Mostly the problem is that in batteries, current flow is not by electrons as in something like a copper wire, but by physical movement of ions. Only so many ions can migrate to the right place and perform the right chemical reaction over some fixed time.

10

Yes Sam, there definitely is electric field reshaping in the wire. Strangely, it is not talked about in hardly any physics texts, but there are surface charge accumulations along the wire which maintain the electric field in the direction of the wire. (Note: it is a surface charge distribution since any extra charge on a conductor will reside on the ...

10

There are many reasons for this situation. Power produced is non-adjustable. The battery produces power at nearly constant rate (slowly decaying with time). It cannot be increased and if not consumed (or stored) the power is lost. (Mentioned by DumpsterDoofus) low power density. ${}^{63}\text{Ni}$ for instance produces ~5 W/kg (and kg here is just mass of ...

9

A battery generates a voltage by a chemical reaction. There is a class of chemical reactions called redox reactions that involve the transport of electrons, and you can use the reaction to drive electrons through an external circuit. This is the basis of a battery. The battery will continue to provide power until all the reagents have been used up and the ...

9

First, your camera is not designed to work with batteries below a certain voltage. When it detects an excessively low battery voltage it turns itself off. That circuit stays in the "off" state until voltage is completely removed from the circuit. When you operate your camera, the current required by your camera varies according to what you do with it. So ...

9

The resistance of water, even with ions and minerals and such, is still fairly high. So, a tiny current flowed through the water, but not very much. Additionally, the heating effect that often destroys them when short circuited would also be nullified by the cooling water.

8

I've just sacrificed an AA manganese alkaline battery to the cause of physics. When I first shorted the battery it produced a current of about 9.5 amps, which I thought was actually pretty impressive. However over the course of 30 seconds the current dropped to around 5 amps. The battery got pretty warm, though I don't think it would have set fire to ...

8

Electrons that reach the positive terminal indeed remain there. The potential difference between the two terminals pushes electrons from the negative anode toward the positive cathode. When an electron reaches the cathode, it stays there to equalize the original charge imbalance between the two nodes. When electrochemical redox reaction sustaining the ...

6

One alkaline AA cell has about 11 kJ of energy. For a laptop battery, it is 360 kJ. Chevrolet Equinox Fuel Cell has 58 MJ of energy. One kilogram of TNT carries about 4.184 MJ of energy. Divide the numbers from the previous paragraph by this constant to see that the AA cell, laptop battery, and electric car battery have 2.6 grams, 86 grams, or 14 kilograms ...

6

Typically batteries involve using the energy stored in some chemical compound (for example, we have batteries of type Lithium-ion). So what happens is we use the potential energy stored in the chemical as an electromotive force to power our device. Now what happens when allt he potential energy stored inside that compound runs out? We have to recharge it. ...

6

Once the battery is fully charged it will not accept any more energy (current) from the charger, since all the energy levels that were depleted when empty are now at their highest level. For example in a Lithium ion battery when all the ions have arrived at the proper electrode the resistance to more current becomes very large, but not infinite since there ...

5

Crazy Buddy's answer and related comments have made the point that you could indeed use a capacitor to charge a battery, but the amount of energy stored in capacitors is generally less than in batteries so it wouldn't charge the battery very much. However there is a new generation of capacitors called ultracapacitors that are being developed with electric ...

5

I am going to assume what you are thinking about is some sort of power pack that uses AA batteries like this one. There is no physical reason that you can not use AA batteries to charge a cell phone, as long as you have the correct adapters. What might be confusing the issue is that Li-ion batteries have definite charging issues. If overcharged, they can ...

4

An ampere passing through your heart can give you a heart attack. An ampere passing through a wire will not. The human body has a fairly large resistance ($10000\ \mathrm{\Omega}$ perhaps?), so the same voltage that can make a large current pass through a copper wire will not necessarily make any significant current flow through a person.

4

What you are describing is called a series connection. Think of the batteries as pumps, with each pump generating 1.5 PSI. If you connect the outflow of one pump to the inflow of another, then overall the two pumps are going to generate 3.0 PSI. Note that the current capability is not doubled. If the two pumps are each rated for 1 gallon/minute, then the ...

4

The battery has in both cases the same energy content, so it just depends on which method uses more energy per time. This power depends on the resistance $R$ you use to connect both terminals, with a given voltage $U$ derived from Ohm's law: $$P = U^2 /R$$ So, the smaller the resistance, the faster your battery will lose it's stored energy. The copper wire ...

4

Sometimes dead batteries will return to life if the are shaken. This only works for batteries that have liquid energy storage chambers. I have never heard of it working with AA batteries before, but I haven't heard of a lot of things.

4

Consider for a moment, a cell that is not connected to a circuit, i.e., there is no path for current external to the cell. The chemical reactions inside the cell remove electrons from the cathode and add electrons to the anode. Thus, as the chemical reactions proceed, an electric field builds between the anode and cathode due to the differing charge ...

4

For low current applications that are sensitive to voltage, like modern electronics, the resistance of the contacts can be significant. So when you reinsert the batteries you clean off any dirt, moisture or corrosion on the contacts, the resistance drops. So when a current flows the voltage drop accross the contacts is reduced and more of the battery ...

4

The article you refer to is about the electrolytic splitting of water. A 100% efficient electrolytic cell would require a voltage of about 1.23V to split water, but for various reasons a simple electrolytic cell requires about 1.48V. The difference between the voltages is called the overpotential, and it increases the amount of power needed to split the ...

3

A battery is effectively an electron pump. Inside the battery a chemical reaction (typically a redox reaction) pumps electrons from the cathode to the anode. If the two ends of the battery aren't connected to anything there's nowhere for the electrons to go and the reaction stops. When you connect the battery to an external circuit the reaction resumes and ...

3

This image should help you understand. As you can see parallel combination increases area but not plate separation. And series combination increases plate separation and not area. Since you understand the rest of the required concept, I would not rid you of the joy of finding out the answer yourself!

3

the voltage through a and b at the start instant should be equal to the original voltage of the battery 240V. To be sure, it's the voltage across a and b, not through - voltage is across, current is through. However, how can we determine whether Vab is +240V or -240V? Kirchoff's voltage law. The KVL equation for this series circuit, assuming ...

3

No, there won't be any persistent current going through the resistor. There will only be some current for a tiny period of time. This will bring the poles of the left battery to potentials $0,V_1$, and those of the right battery to $V_1,V_1+V_2$. Note that the electrostatic potential of both poles of the two batteries that are connected to the resistor will ...

3

As I mentioned in a comment, the electrical conductivity of tap water is pretty low, so while current definitely did flow while underwater, it was only a small amount, hardly enough to drain the battery. You can actually measure the current using an ammeter if you have access to one.

3

Apparently Hydrogen/Oxygen are liberated when a Lead-acid battery is charged NOT Always. Just explaining how? Lead-Acid Battery comes under Secondary cells. An LA battery usually has plates of lead & lead oxide (when fully charged) or lead sulfate (when fully discharged) in an electrolyte of 35% sulfuric acid and 65% water solution. Indeed, ...

3

Internal resistance generally increases as you lower the temperature. This is because batteries generate current using a chemical reaction and the reaction generally goes slower at lower temperatures. This article on Wikipedia claims the internal resistance of a manganese alkaline battery increases from 0.1 ohms at 40°C to about 0.9 ohms at -40°C. Car ...

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