# Questions tagged [batteries]

Devices to store chemical energy and convert it to electrical energy.

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### Why do we use capacitors and not batteries in defibrillator?

Why do we use capacitors in defibrillators and not batteries? I know that capacitors are used to store electrical energy but isn't the function of a battery just the same? Moreover, I know that ...
49k views

### Does the mass of a battery change when charged/discharged?

If so, how much? Is it possible to detect it, or is it beyond any measurement? I'd say there are two possible scenarios (depending on the battery type) and both seem interesting: The battery reacts ...
8k views

### Why do 'dead' batteries work again after exchanging the places of the batteries in an electronic device?

My camera, which is powered by two AA batteries in series, would not power on. I removed the batteries, exchanged their locations, and the device worked again - for another 15 minutes or so. The ...
9k views

### How can a battery charge up another battery to a higher percentage?

Say I have my phone on 5% and a large battery pack on 35% and I charge the phone. By the end the phone is on 100% and the pack is on 12%. How can the battery pack charge the phone up to a higher ...
783 views

### Why can't batteries be charged quickly?

Charging of laptops, cell phones take so much time. Why can't we make such batteries easily/commercially which are charged more quickly? What's the thing behind this limiting?
118k views

### Different batteries connected in parallel

If we have 2 batteries one of emf x and the other is of emf y and we connect them in series we get an effective emf of x+y. But what if we connect them in parallel, how to calculate the emf now?
41k views

### What happens when we connect a metal wire between the 2 poles of a battery?

As I remembered, at the 2 poles of a battery, positive or negative electric charges are gathered. So there'll be electric field existing inside the battery. This filed is neutralized by the chemical ...
3k views

### Increase in mass of battery of my smartphone [closed]

The charge on my smartphone was zero. I charged my phone to its maximum capacity. How much mass $\Delta m$ did my mobile gained after charging the battery? Maximum capacity of the smartphone's ...
240 views

### Theoretical physics for better batteries?

It is Earth day, so I started thinking about the theoretical physics problems that could help reduce greenhouse-gas emissions and fight climate change. We actually have a reasonable range of ways to ...
4k views

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

Suppose pH of water is $6$, I think this means there is one $\text{H}^{+}$ ion for every $10^6$ water molecules. When we plug in the battery, I believe we see a current as the $\text{H}^{+}$ ions ...
56k views

### What is the difference between a battery and a charged capacitor?

What is the difference between a battery and a charged capacitor? I can see lot of similarities between capacitor and battery. In both these charges are separated and When not connected in a circuit ...
676 views

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

I can't for the life of me figure this out. I feel like i'm missing some crucial detail about how batteries work. Imagine two batteries connected in series, like this: ...
15k views

### Why aren't betavoltaics and alphavoltaics batteries widely used?

Betavoltaic batteries are devices which creates electricity from beta radiation of a radioactive material. Alphavoltaics operate similarly, using alpha radiation. The concept was invented roughly 50 ...
50k views

### Why do two connected 1.5-volt batteries become a 3- volt battery?

Why two connected 1.5 volt battery become 3 volts? If one battery plus side is connect to minus side of another battery, there should be a current flow between them until no free charge move anymore, ...
37k views

### What happens if I throw a battery into water?

Today I have by accident thrown a AAA battery into a bucket of water. I fished it out of the water immediately (within 20 seconds or so) and nothing notable had happened and the battery is still full ...
4k views

### What maintains constant voltage in a battery?

I know there's lots of questions that address similar situations, (Batteries connected in Parallel, Batteries and fields?, Naive Question About Batteries, and the oft-viewed I don't understand ...
119 views

### Why are(n’t) rechargeable batteries damaged by partial charging?

Originally asked in ElectricalEngineering.SE, but I was told Physics.SE might be a better place to ask. Over the years, I've come across websites and people with different opinions on the "correct" ...
16k views

### Path of an electron through an electric circuit

When a potential difference is applied across a conductor, and if an electron moves from the negative terminal of the battery and reaches the positive terminal, then I want to know if the electron ...
11k views

### Can single DC 1.5V battery generate 1500 watts of power?

Suppose there is a DC $1.5\mathrm{V}$ battery connected with $1.5\times10^{-3}\mathrm{\Omega}$ resistor. Then the amount of circuit current is $I=V/R=10^3\mathrm{A}$. (according to Ohm's law) I know ...
6k views

129 views

### Nernst Equation and Energy

I have a question regarding the Nernst equation and energy in a system. I know this is also a chemistry question, but I was interested in the thermodynamics (the energy of a system), so I decided to ...
1k views

### Physical interpretation of circuit with battery charging capacitor

In the picture below, we are charging up the capacitor, by connecting it (and the resistor to a battery of voltage $V_0$, at time $t = 0$). In terms of what is happening physicially, how would you ...
16k views

### short circuit an alkaline battery

i'm not doing anything related to physics, but i'm just curious : What really happen when i short circuit an alkaline battery ? some article in the net shown that fire/explosion can be happened when ...
510 views

### Will the two capacitors be charged in this circuit?

Is such a circuit possible to exist with the two capacitors charging? Because if we considered the outer loop using Kirchhoff's law we get: ℰ = q1/C1 + q2/C2 But since the two capacitors are ...
2k views

### Why is the voltage of a battery equal to the emf?

We know that there is an electric field inside the battery that works against the moving electrons of a circuit. But there is also the chemical force of the battery that at some point become equal. ...
345 views

### What happens when electrons reach the battery?

We have a capacitor which is connected to a voltage source. The top plate of the capacitor is connected to the positive terminal of the source. Therefore, electrons go from the top plate to the ...
3k views

### Why batteries in serial don't discharge each other?

A question that I've asked myself for long time about why batteries in series work as they do. I'll try to explain: If you take two batteries, let's say A and B, and you put A's anode touching the B'...
2k views

### What's the difference between Capacitors, Ultra-Capacitors and Batteries

Capacitors are known to hold and release energy very quickly, unlike the slower release that batteries exhibit. If one were to bunch many (1000's of) capacitors together could they function as a ...
11k views

### How can a circuit function with two negative battery terminals facing each other?

Here is a drawing of the circuit that is confusing me: I don't quite understand how batteries work in this diagram. If a battery has a negative and positive terminal, there must be a barrier ...
2k views

### Charging of a battery

A battery has an Emf 6 Volts. It is completely discharged. It is charged by maintaining a potential difference of 9 Volts across it. If the internal resistance of the discharged battery is 10 ohms, ...
413 views

### Do battery electrons only move if there is a positive terminal at the end of the wire?

I'm sorry if this question may seem wrong in many cases. What would happen if we had a wire with the length of 1 kilometer that connected the two terminals of the battery? Do electrons care if the ...
4k views

### Why electrons flow through a wire connected to a battery?

I would like to know why does electrons flow through a wire connected to a battery as said in AC/DC: What's the Difference?.It tells that "the electrons that are stripped from the carbon electrode is ...
1k views

### Why does not a battery kept in empty space discharge on its own? If space between the terminals is empty, what prevents the electrons to flow?

Given here is the picture of a twisted battery kept in free space (vacuum). Will the battery discharge quickly? I mean, it should discharge faster than it would if we were to connect the terminals ...
156 views

### Creating permanent magnets with minimal resources?

Okay, so this is kind of a goof-off question, but it's part of an of educational game that I've been playing with myself for years. If you don't want the background then skip to the horizontal rule, ...
8k views

### How can you calculate (or convert) the Wh of a capacitor whose energy is given in Farads

When trying to compare the energy in a battery to the energy in a capacitor, the units don't match up. How can one compare a battery whose Ah are 10 and Voltage is 3 (for a total of 30 Wh) to a ...
606 views

### Why do batteries work?

Consider diagram A. In diagram A a car is at the top of a cliff. Gravity is pulling it down, but it does't move since its on a flat surface. Even though it would be at a lower potential at point B, it ...
779 views

### Why are charging times so long for Lithium-ion batteries?

Why do rechargeable batteries (e.g., mobile phone batteries) need sometimes several hours to be fully charged? In other words, what are the physical constraints that don't allow me to charge my iPhone ...
4k views

### If I charge a battery using a much higher current, can it explode?

If I have a 12V 4Ah lead acid battery and use a battery charger that, let's say for example, can charge 10A, 50A, or 100A. If I theoretically turned it to 100A will the battery explode? I understand ...
254 views

### Does the internal resistance of a battery dissipate heat as expected?

A common real battery is often modelled (to a good approximation) as a perfect voltage source having emf $\varepsilon$ with a series internal resistance $r$. So, when a current $I$ is drained from it, ...
I have this setup. It consists of a battery of no internal resistance with voltage $V$ and a resistor with resistance $R$. It also consists of a voltmeter of some (not so large) resistance as good ...