# Questions tagged [batteries]

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

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### Deriving a function that equals the battery percentage of a laptop after t minutes have passed when a laptop is plugged in [closed]

Basically, I wanted to derive a function which could model battery percentage as it's plugged in(Assuming the laptop starts off at 0%) using the charge differential equation for a capacitor. Solving ...
46 views

### Power delivered to a Resistor is $V^2/R$. Does size of battery matter?

I had connected a thin Resistor wire to series combination of six coin cells or to a small sized 9V battery. The wire got hot in a normal way BUT when I connected the same resistance wire to a large ...
56 views

### Voltage across a capacitor in a circuit [closed]

I'm trying to find the voltage across the capacitor when it is fully charged in the attached diagram, I haven't done a problem like this before and I'm quite confused on what I am supposed to do to ...
51 views

### Diode confusion

Consider the following diagram Here, the diode is in forward bias, and allows current to flow. However, I am slightly confused why this is the case. A diode is defined to only allow current to flow ...
31 views

### Determining if a capacitor will charge or discharge based on voltage [closed]

The question also says that the voltage of the battery is 12 V. We're supposed to determine if the capacitor is charging or discharging or neither. I'm just not sure how to use the voltages given to ...
44 views

### Weird Potential Divider Diagram

How does the above circuit work? My textbook only has potential divider circuits such that there is only one output voltage. Such as this one. Could we replace the arrowed line in the uppermost ...
60 views

### Potential Divider Circuits

Consider the following circuit: From my understanding, consider the series circuit without the $V_o$ part. The voltage must be used between resistors $R_1$and $R_2$. We know $V=IR$ from ohms law. As ...
1 vote
103 views

### When a circuit with three lights goes from series to combination, with one on the main loop and two on different branches, does power in branches $↓$? [closed]

I am considering a circuit with three light bulbs. When a series circuit goes to a series-parallel circuit with one light on the main loop and two on different branches, the total resistance decreases ...
95 views

### How to know if resistors are in series? [closed]

According to Fundamentals of Electric Circuits, 6th edition, Alexander & Sadiku, p. 36 Elements are in series when they are chain-connected or connected sequentially, end to end. For example, two ...
38 views

### Multiple batteries in a capacitive closed circuit [closed]

In the photo I added,there is a question as you can see and its given solution. When the switch S was open, charge on each capacitor was calculated and the voltage was taken as the net voltage of the ...
1 vote
48 views

### Mismatching Batteries of Different Voltages

Consider connecting two batteries of different voltages $x$ and $y$ in parallel. Considering a series circuit, the total voltage would be $x+y$. However what happens in this parallel case? From my ...
119 views

### Do chargeable batteries break the third law of newton? [closed]

When you charge a lithium battery for instance the electron momentum that coming out of the source is stored in the battery. The problem is that the direction of the electron might change when ...
49 views

### Capacitance and the battery connection

In the photo I added there is a question and its solution (given). It has been written at last(as I highlighted) that 'in order to get the minimum capacitance, dielectric should be removed and battery ...
31 views

### What is "capacitive effect" in terms of battery research?

For example, the paper I am reading states that the current was "periodically interrupted without changing polarity" to "demonstrate that the peaking behavior is not due to a capacitive ...
63 views

### How do the nodes affect the circuit?

I am tasked to simplify this circuit to one source and one resistor, which is equivalent to the original but obviously easier to solve. My problem is the fact, that I don't know how the nodes A and B ...
942 views

### How could one measure the capacity of a battery with one instantaneous meter reading?

My car battery when fully charged operated the car lights and air conditioning for a few minutes (without the engine being on) before it was not powerful enough to operate the starter motor. The ...
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### Is there a theoretical limit on the charging speed of a lithium ion battery? [closed]

I'm wondering about lithium batteries in electric cars. Could time and technology improvements continue to improve charging speed, to the point where you could "refill" an electric car as ...
46 views

### How to calculate the total resistance? [closed]

So I am new to physics and I am trying to solve the total resistance of this circuit. My question is: because there is a battery in the same branch as R2 and a Capacitor in the same branch as R3, when ...
50 views

### Simple $RC$ circuits

I have a $RC$ circuit with a capacitor (capacitance$=C$) uncharged initially and resistor (resistance$=R$) in series with the battery of EMF $E$. Assume its internal resistance to be negligible. Now ...
1 vote
84 views

### Why do my Milwaukee batteries weigh different amounts when charged vs uncharged

We use m12 small sized Milwaukee battery’s and I noticed when I use them I feel like they weigh different when using them sometimes while using them and then I read a article about batteries loosing ...
27 views

### Is anode to cathode ion movement due to binding energy and electrostatic field?

I'm trying to understand exactly what chemical and physical effects oxidise the Li atoms and make Li$^+$ ions move from anode to cathode on discharge, and to find numbers in terms of electrode ...
1 vote
130 views

### Why is the emf of the battery which is being charged included for the current flow?

When a battery is being charged, let's say it has an emf $\mathcal{E}$ and internal resistance $r$. At first it's completely drained, and we use a battery to charge it back, and lets say the emf of ...
1 vote
263 views

### Gravity battery output calculation

Let’s assume I lift a 1 ton weight to 20feet high. To calculate the amount of potential energy stored in a 1-ton weight (2000 pounds) lifted to a height of 20 feet, Potential Energy (PE) = mass × ...
97 views

### Is there really no Cranking Amps formula?

I am looking for an apparently non existent physics formula (see below) so that I can very roughly (+/- 25%) calculate the Cranking amps (CA) of a SLA (sealed lead acid) battery. I want to use the ...
1 vote
71 views

### Why does changing redrawing this circuit in the new way work?

I was doing a circuits question and the mark scheme showed they had redrawn the circuit in a new way but I didn’t understand why part of the old circuit was equivalent to the new one. I understand ...
1 vote
192 views

### Potential difference across the terminals of a battery with internal resistance

The potential difference across the terminals of a battery with resistance is equal to the emf when there is no current.But when there is a current there the potential difference decreases or ...
1 vote
63 views

### Why wouldn't current flow if a circuit is connected between batteries but the other ends of the batteries are disconnected?

This light bulb is connected between positive and negative terminals, but no current flows. Why does this not work?
1 vote
78 views

### Confusion regarding voltage drop in circuits

In electrostatics we were taught that Voltage drop is the work done by an electric field in bringing a unit charge from point A to point B. Or $V= E.d$ where $d$ is the displacement between A and B. ...
80 views

### Why do we get a null point in potentiometer or meter bridge?

Why do we get a null point in potentiometer or meter bridge. I mean the battery is connected so current should keep flowing through the circuit. So why do we get a point where no current is flowing as ...
1 vote
41 views

### Why does my microwave turn on other battery powered electronics?

Situation: I have a 8-10 yr old LG microwave in a small alcove built into the cabinetry of our kitchen counter. I have a pretty cheap Bomata battery powered coffee scale that I store on the countertop ...
45 views

### Current flow trough capacitors at $t=0$ [closed]

I'm bit confused about the current flow in capacitors. My question is, let's assume those two electric circuits: As shown in the picture, the only difference is only the capacitance. I'm wondering ...
86 views

### Why do I measure 0 V between the negative pole of a battery and the ground?

I today confused the entire company (we work on batteries for trains) when I stumbeled about the following fact: When you touch the negative pole of a battery having electromagnetically isolated shoes,...
912 views

### Does the EMF of a battery change with time?

OK, so... I know that batteries provide less and less energy with time. My question is- is that a result of a decrease in the EMF of a cell or an increase in the internal resistance of the cell or ...
82 views

### In a simple DC circuit does the surface charges on the wires influence the field of capacitor?

we know that in a simple circuit (a battery and a resistor) the battery induces surface charges on the surface of the wire such that the net electric field due to battery+surface charges inside the ...
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### Black Hole Battery [duplicate]

What is the maximum charge/discharge efficiency of a spinning black hole when used as a battery via frame dragging effects? Charging: I'm pretty sure the best way to add to its angular momentum (in ...
196 views

### How do electrons from a battery move through a circuit? [duplicate]

I'm reading a book called Practical Electronics for Inventors and it describes the method by which batteries generate electron flow as follows: the battery releases a few electrons via a chemical ...
77 views

### Why is charge surface uniform while circuit is open?

The above image shows surface charge distribution for open circuit(ends not connected). I point out different regions by numbers. The surface charge distribution is mostly uniform(maybe, not near the ...
53 views

### Understanding section on electromotive force in Purcell and Morin's Electricity and Magnetism

I am following the book Electricity and Magnetism by Purcell and Morin. There is a section on the electromotive force that I would like to understand better. I will write out the snippets from the ...
265 views

### How does battery make charge in conductor move?

A wire with resistance is connected to the two ends of a battery, how does the battery cause the free charges in conductor, the wire, move? I know the battery provide a potential difference. But how ...
2k views

### Why does voltage increase in a series circuit?

I'm just starting electronics and I find myself not understanding voltage at all. In a simple circuit, let's say a 1.5V battery connected end to end it's easy to see how there's a 1.5V drop. However ...
748 views

### Why does a short circuit occur? [duplicate]

For example, if you have a battery and you connect both ends with a short circuit with zero or low resistance, why does it short circuit? What causes this internally? What are really happening with ...
106 views

### What do these lines mean?

I am currently reading about emf and internal resistance and I came across this paragraph. What does this mean?
4k views

### How do batteries lose capacity in winter?

One problem of electric vehicles is that the battery capacity often shrinks under low temperatures. Some batteries can lose as much as 50% of capacity in winter. What I don’t quite understand is how ...
33 views

### Electrical power in series and parallel [closed]

I have confused myself massively and would like some help. In my situation we have a cell with emf $V$ and no internal resistance, we hook up 2 lamps of resistance $R$ ohms in series, I have ...
32 views

### Charge a battery with a capacitor

Though the opposite is readily found, battery charging a capacitor, I am looking to scavenge small generation capacities to charge a battery. Things like piezoelectric effects or collecting ...
497 views

### How does a voltmeter connected in series to a cell/battery measure the EMF?

I am a bit confused about this idea. When ONLY a voltmeter is connected to a cell, there is no current flow since the voltmeter has infinite resistance. So, the voltmeter gives the reading of the ...
65 views

### How does a voltage source know what intensity to give? How much time does it take to measure and know? [closed]

as the title says, how does a battery use V = IR in measuring the intensity it would give, or is the voltage the variable here? if it's the voltage, what does that even mean?
202 views

### Charging a capacitor with a battery

I'm trying to better understand the process of charging a capacitor with a battery. My textbook (the Halliday's Fundamental of Physics) describes this process in these terms: When the circuit [...] ...
$\newcommand{\d}{\mathrm{d}}$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 ...