# Questions tagged [batteries]

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

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### How do you determine the electromotive force when the negative plate of the capacitor is connected to the positive terminal? [closed]

$\newcommand{\d}{\mathrm{d}}$We have a square wave source with period $T$ and voltage $V_0$ connected to a circuit which is has a resistor of resistance $R$ in series with an uncharged capacitor of ...
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### How is 'exactly all' the energy of battery converted to thermal energy?

When charges flow in a simple circuit, then if 5C of charge is transported by the battery(of 5V) in some time, then the work done/energy lost by the battery is 25Joules. During this time, the ...
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### Voltage and electron flow in battery

I just had a few confusions with battery voltage and overall how it worked. I tried searching online but the answers were so general they didn't explain "why". To start when we are using up ... 24 views

### Why is the observed voltage 5V when the power supply is 18V? [migrated]

I am building a headlight driver circuit for my solar car team at school. The circuit uses transistors to drive the headlights and an 18V power supply. My HIGH and LOW signal is a 5V signal and 0V ...
665 views

### Why does a bulb not glow when one terminal of a bulb is connected to the negative terminal of a battery and other is connected to the ground?

I am a high school student and has been wondering a while about this: Why does a bulb not glow when one terminal of a bulb is connected to the negative terminal of a battery and the other is connected ...
38 views

### Entropy of Mixing in Lithium Batteries [closed]

The class is going over lithium-ion batteries and I’m honestly lost. We have an assignment about modelling Li-ion batteries and we have to show how $$\tag{1}S=k_b \ln[N!/(n!(N−n)!)]$$ Using Stirling’s ...
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### Parallel circuit Question [closed]

Re Question on why bulbs in battery powered parallel circuits get brighter when one or more are switched off or removed … understand the reasoning but why doesn’t this happen in a household light ...
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### Potential drop against internal resistance of cells in combination

Suppose two cells of emf and internal resistance e1, r1 and e2, r2 respectively are connected in series. The negative electrode of 1st cell is connected to negative electrode of the second cell. Why ...
42 views

### How is voltage generated and maintained in a circuit?

I recently discovered this answer which explains how batteries maintain a constant potential difference. So what I understood was that batteries spew out electrons on the cathode, and by doing this ...
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### Current when inductors charging in parallel are discharged in series

We started discussing DC RL-circuits in class and were analyzing the following circuit The scenario is the switch has been closed for a long time so the current through both 2-ohm resistors is the ...
133 views

### Is it possible to have positive current coming from ground?

Is it possible to have positive current coming from ground? This is only in physics land and ignores all real-world situations.
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### Charge distribution on a system of 3 capacitors when the middle one is earthed

Three conducting sheets 1,2 and 3 are placed parallel to each other such that separation between them is negligible. Sheet 1 and sheet 3 are given charges $+Q$ and $+3Q$ respectively. $Q=3 \space mC$ ...
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### Why doesn't passive cell balancing re-distribute electron charge?

I've done a lot of searching for an answer that's just eluding me. To put it simply, when series batteries are balanced using a passive balancing scheme (resistor and FET), why don't the electrons ...
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### What’s happening with ions while a capacitor is being charged by a battery?

An uncharged capacitor has an equal amount of positive and negative charges in both plates, meaning there are ions in both plates which altogether have a neutral charge. When you connect an uncharged ...
209 views

### Problem with Faraday's Law for a Circuit with Battery

From Maxwell's equations, we know, \nabla \times \vec E=-\frac{\partial \vec B}{\partial t}\Rightarrow\oint \vec E\cdotp d\vec l=-\int\frac{\partial \vec B}{\partial t}\cdotp d\vec a \tag{1}\label{1}...
1 vote
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### Electromotive force is independent of path?

I am having some trouble understanding the EMF and how it provides a steady current (that is, the current isn't weaker further from the source). My present understanding is that if we have a battery ...
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### How is the potential energy of electrons conserved and increased in series wired batteries? [duplicate]

Suppose we have a simple series circuit with a resistor and 2 batteries of rating v0 - battery 1 and battery 2, connected in series. Battery 1's positive terminal is connected to the circuit and so is ...
38 views

### Ni-Cd Battery discharge circuit model [closed]

I am struggling with deriving a set of equations to represent mathematical model of Ni-Cd battery, so would you give me a through explanation and proper textbook/reference articles.
1 vote
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### In real life, which remains the most constant: voltage, current or resistance?

According to ohms law, V=IR, where R is constant If the resistance of a circuit changes due to change in its physical conditions like temperature, etc. What will change-current or voltage?? Does the ...
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1 vote
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### What if there's no potential difference in LED bulb (not in battery)? [closed]

If there is potential difference in battery why we need potential difference in LED bulb
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### Very simple question, does a resistor have potential difference across it even when there is no current going through it? [closed]

Assume a circuit with a battery, resistor, and capacitor in series. When the capacitor is full and no charge/current is going through the circuit, is there a potential difference across the resistor? (...
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1 vote
153 views

### About a battery's positive terminal

Does the positive terminal of the battery mean that the concentration of electrons is more there. In some places people say that current moves from positive to negative and they call it a convention ...
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### Why does a car battery make such violent sparks, yet it it's safe for me to touch both terminals?

YouTube videos have assured me that it's safe to touch the terminals of a 12V AGM car battery with my bare hands. They even claimed it'd only be a tingle if I connected wires to the terminals and ...
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### How different material capacitors can develop different charges?

I learned in a video tutorial that same battery could produce different charges based upon different capacitance of the materials used. Also A capacitor fully charged has the same voltage as the ...
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### Is the Voltage of battery equal to voltage of resistor only in ideal circuits?

Has the saying" voltage of battery is equal to voltage of resistor" got something to do with the fact that ideal circuits are thought to have no resistance? Is it just a way of saying that ...
148 views

### Is "series opposed" a correct term for automotive charging of battery? [closed]

What is the definition of "series opposing circuit"?
105 views

### Can I arbitrarily pick which resistors I should calculate the equivalent resistance with?

Let's say I have some random complex circuit of resistors. Maybe something like: Now I wanna calculate the equivalent resistance of this whole circuit. Can I just randomly pick which resistors I ...
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1 vote
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### Why can't I observe a voltage between two capacitor plates when only one of the plates is connected to a battery?

Let's say I have a battery and a capacitor that is neutral. Now I connect the battery positive terminal to only one plate of the capacitor. From what I know, there is a potential difference between ...
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### Cells in parallel combination

This is an excerpt from my book and I am not able to understand how could “V” be equal to Ε1- I1r1 as well as Ε2- I2r2. I mean One battery could have emf of 50 volt and another just 5 volt. So, How ...
1 vote
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### Working of battery in circuit

The battery has a potential difference. So, shouldn't battery generate an electric field directing from the positive side to the negative side? If that's the case, we know that potential in a wire(...
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1 vote
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### Potential Difference across two cells in series

I studied yesterday that total potential difference across two cells in series is simply the algebraic sum of potential difference of those two cells. And by which logic it has been proved, I am ...
1 vote
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### Does a battery store store charge? Do we give it charge when we charge a battery?

NOTE: I'm not requesting a solution to this problem; rather, I'm seeking clarification on an objection that arose throughout the process of solving it. In order to refresh my understanding of AC and ...
72 views

### Resistances in series or parallel

In the figure above,we have two cells $E_1$ and $E_2$ and $7$ resistances arranged as shown with $I_1$ current emitting from $E_1$ and $I_2$ emitting from $E_2$. Is it possible to find the equivalent ...
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### The amperage of batteries in parallel configuration

I made a circuit using phet colorado's simulation online, and I have two batteries in a parallel configuration with one light bulb outside the batteries parallel configuration. Note: both batteries ...
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### Capacitor vs Inductor - who wins?

The idea behind the question is to determine which one of the two - capacitor or inductor will drive the current in the circuit when connected in a specific way. Say I have a circuit in which I have ...
1 vote
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### How electrolytes conducts electricity?

While studying electrochemistry, I came across two key points that I'm unable to understand. why does DC alone break down the electrolytic liquid and b) Why doesn't AC do the same?
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### Force on a test charge inside a cell

Considering test charge inside a cell. Let the cell be in an open circuit. I know that a potential difference will develop between the two electrodes of the cell. If I take a test charge and place it ...
1 vote
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### How do batteries in parallel work? [closed]

So I understand that the voltage is the amount of work done per column of charge, so its sort of a "pushing force" and amp are just the charges per second, or "amount of stuff per ...
1 vote
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### How do I find value of $I$ using Node Voltage analysis method? [closed]

How do I find value of current $I$, using Node Voltage analysis method ?
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### How to derive Thevenin Voltage formula using Kirchoff laws?

Here's a simple voltage divider. I'm learning Thevenin Circuits now and we use the formula for Thevenin Voltage a lot (very useful!) but I'm not sure how the formula arises. My professor said I can ...
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### What effects do inductors have on circuits?

The above diagram is a simple circuit containing an inductor. According to the right hand grip rule, it can be deduced that the magnetic field is to the right. But the magnetic field produced by the ...
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### Why short circuit doesn't takes places in a homopolar motor?

In a homopolar motor we directly connect copper wire to a battery without any resistance with a magnet in bottom, so why doesn't a short circuit takes place?
1 vote
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### If resistance in an electric current is 0 (ideally) then would there even be current flow?

From my understanding batteries are used to charge electrons with electric potential which they then use to do work on resistors in a circuit. After doing work the electrons return to the opposite ...
1 vote
148 views

### Circuit resembling wheatstone bridge but not exactly [closed]

The below circuit resembles that of two individual wheatstone bridge arrangements as the ratio of resistances satisfy the conditions however we cannot come to this conclusion as potential at one end ...
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1 vote
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### The current in an $LR$ circuit [closed]

I am trying to understand $LR$ circuits better. I am under the impression that inductors are resistant to change in current. So, the premise here is that the circuit was switched to side 1 for a long ...
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### A question regarding determining internal resistance of a cell by using a potentiometer

In the given figure at null point J current does not flow through JD and AC but current does flow in the second circuit CDEF and primary circuit.My question is why doesn't current flow through ACFED ...
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1k views

### Gravity train with the help of batteries?

Imagine a gravity train (https://www.math.purdue.edu/~eremenko/train.html) that goes through Earth's crust from point A to B. The train could advance through the ride just by the force of gravity and ...
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### How can I safely heat up a AAA battery? [duplicate]

I’m working on a science experiment in whether or not the temperature of a battery affects how long it will last. It’s the middle of winter where I am and I’m not quite sure how to safely heat up the ...