Questions tagged [batteries]

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

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2answers
118 views

$E=mc^2$ tells us that everything has energy. So why can't we use anything as a battery/power source?

My body has mass, the floor has mass, the air has mass. According to the formula E=MC2, we can get insane amounts of energy with very very very small mass (looking at you antimatter). However our ...
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2answers
68 views

Bike light: what consumes more current, continuously on or blinking?

I've been riding my bike many nights wondering the following question: What consumes my LED bike-light battery: the continuously on setup or the blinking setup? It might seem trivial, since the ...
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4answers
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 ...
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1answer
771 views

If a battery is open on one end but connected on the other, does it raise the potential on the connected end?

If a battery has one end open and other end connected to a circuit will the battery increase the potential at the point of connection?
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1answer
9k views

Relation between Terminal Voltage and EMF of a cell while the cell is being charged

I know the relation between the terminal voltage, V and emf of the cell, V' while charging given by V = V' + Ir where I = Current in the circuit and r = Internal Resistance of Cell Can anyone ...
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5answers
2k views

Can a capacitor be charged without having resistance in the circuit?

I was looking for the fact when a capacitor is directly connected to battery without resistor what will happen? If possible then tell the time for charging.
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1answer
95 views

What resistor should be connected to a $12\,\rm{V}$ battery for a $9\,\rm{V}$ output?

I have a $12\,\rm{V}$ car battery and a $9\,\rm{V}$ toy piano. I want to power the piano through the battery but the voltage is too high. What resistance should be connected to this circuit so that ...
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1answer
49 views

I need a 12V battery supply for a device can I just connect four 3V batteries? [closed]

its for a modem which requires a 12v adapter, 1amp. So I tried connecting 4 batteries and also 5 but it never turned on and I couldn't figure why?
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1answer
66 views

What's a reasonable difference in resistance between batteries in parallel?

I know that the differences in resistance between batteries in a circuit will create different drop, and as a result draw unequally. Unfortunately, I couldn't get my hands on a parallel D-cell ...
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3answers
2k views

Current flow with batteries in series vs parallel

Taking let's say three ideal and identical batteries, why does the current flow increase when we add them in series compared to them being in parallel? I can understand the height analogy for voltage ...
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2answers
4k views

Energy loss due to internal resistance of a battery?

Say I'm using a battery to power some process, and the internal resistance of the battery is given. The resistance of the process is not given, but assume it is minimal so the circuit runs at maximal ...
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1answer
134 views

Can a capacitor be charged with multiple batteries connected in series [closed]

I connect 2 9-volt batteries in series. Then I connect that to a capacitor. Will that then charge the capacitor to 18 volts?
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1answer
733 views

How does the voltage source provide energy in a circuit?

I understand that a voltage source drives the current to flow from the terminal with lower potential to the terminal with higher potential. However, if the electrons are gaining potential energy then ...
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2answers
80 views

Can an electric car be usefully powered (or at least supported) by solar energy?

There are cars on the road that run on electricity instead of gasoline. And that's great, it really is. But you have to charge them, which is a problem if there are no charging stations in your area....
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5answers
334 views

Many cells in parallel

If two or more cells of unequal voltages are connected in parallel (with the same terminal on the same side), is there a formula that gives the net potential difference? Also, by Kirchoff's loop law, ...
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1answer
71 views

Why does all the voltage has to be dropped in a circuit?

In a simple circuit with a single resistor the entire voltage provided by the cell drops. It is independent of the resistance. Why does this happen? What is the mechanism behind this? I mean why does ...
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1answer
181 views

How the current moves in the battery and outside the battery?

Does it move again to the negative terminal or stays at the positive terminal until the electrons all come .so the voltage will.be zero and current flow .I want simple clear explanation because i am ...
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2answers
487 views

If two batteries that are fully charged with opposite polarities and one has higher emf.Does one will charge the other? [closed]

if there are two batteries fully charged in a circuit connected in series and one has higher emf than the other does one charge the other or not ? does any current pass in the circuit ?and if yes ...
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0answers
165 views

Quartz piezoelectric battery

I'm designing a battery that uses quartz crystals to hold/produce a current for a long time using piezoelectricity. My question is: Would it be more efficient to have multiple small quartz crystals ...
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1answer
152 views

What do the batteries actually do to the electrons?

I am plagued by this simple question that what force exactly causes the motion of an electron in the middle of a lattice of electrons of a wire? a. Is it an electric field created inside a wire due to ...
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1answer
2k views

Connecting cells in series and parallel

When 2 cells is connected in series of the same emf like the following: [just the part of the circuit that I need...] The resultant emf will be twice as the previous identical emf. If we reverse ...
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0answers
55 views

Is this Thevinin equivalent of a voltage divider, correct?

Found the PDF version of The Art of Electronics (Horowitz and Hill) recently, and, having nothing better to do... I thought I'd give it a read. It wasn't long before I hit a wall (courtesy: my inept ...
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1answer
442 views

Why does battery generate less terminal voltage difference when current flows?

The terminal voltage difference of a battery means the difference of voltage between the two termials of a battery. Now, a battery has a voltage at the positive terminal and a voltage at the negative ...
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3answers
2k views

Backwards proof for balanced Wheatstone bridge

We know that in this Wheatstone bridge if, $\bf{I_3 = 0}$, it can be derived that $\bf{\frac{R_1}{R_5}=\frac{R_2}{R_4}}$ . But could we prove it backwards, mathematicaly, that - if in such a circuit $...
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1answer
2k views

EMF of an ideal cell

I know it's a very stupid question but I am confused a little bit right now. An ideal cell has constant EMF of 7V. When connected in a circuit, the voltage across the cell decreases to 5V. Can i say ...
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1answer
309 views

Battery life with hot and cold wires

If a AA battery was kept at a constant temperature and was connected in a simple circuit will the battery drain faster if the wires are kept at a cold temperature or at a hot temperature? I ...
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3answers
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 ...
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2answers
40 views

How is the loop law applicable when I connect a battery with an ideal copper wire?

We would have a potential rise but where is potential drop? Considering wire to be having negligible resistance.
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1answer
1k views

Electromotive force of a battery

The definitions of electromotive force of a cell that i have read include: 1.When no current is drawn from a cell,i.e., when the cell is in open circuit, then potential difference between the ...
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3answers
1k views

Capacitors in parallel final potential difference

I was provided with the following problem. So I first calculated the total capacitance for (i), which was $$4.5 + 1.5 = 6.0 \mu F$$ Now part (ii) is the question i'm struggling at. I know that ...
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2answers
146 views

Why do batteries in series add up in voltage? (real explanation requested)

This has been asked before but I need to be clear on what kind of answer I'm looking for. All the other posts are just water analogies. I get it, you add the voltages together. And there's a magical ...
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1answer
214 views

Not understanding inductor behaviour in RL circuit

This figure from Halliday's book is perfect to go with my question. I've been trying to understand how exactly indutance works almost the entire morning, I think I need another perspective, please. ...
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2answers
263 views

Resistance in internal battery, voltage source

I was reading the post Which dissipates more power, a small or big resistor? and DanielSank's reply said Now, any circuit you would reasonably call a "voltage source" must have a low internal ...
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2answers
481 views

Diode IV experiment

Ive been looking at experiments to look at the IV relationship for a LED, but I see most of them use a rheostat instead of a series variable resistor and my question is, what is the advantage of using ...
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0answers
52 views

Issues reading a paper about batteries

I am looking for answers regarding a paper I am reading right now. I either found stupidly high values or strange SI unit. This paper is about battery charging, and the battery model used brings me ...
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4answers
4k views

How can there be a voltage when there is no current?

I'm told at school that the Electromotive Force (e.m.f) of a battery equals the potential difference between the terminals of the battery when there is no current. How is that possible? How can there ...
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1answer
774 views

Can a mobile phone emit gamma rays? [closed]

I heard that inside the battery of mobile phones (but also of other electronic devices) can happen quantum leaps that cause the emission of gamma rays photons. Is this phenomenon really possible?
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1answer
85 views

Circuits in parallel of different voltages

I've been having difficulty in understanding why the voltage across the resistor $3$ is $10V$. My main problem is understanding why the $12V$ resistor couldnt for example drop $1V$ on the first ...
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2answers
958 views

Adding two same DC voltage source in parallel

In a parallel circuit(imagine two branches),with one DC voltage in a branch and another DC voltage in a branch, what is the method of computing the total DC voltage? The voltage through each component ...
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1answer
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 ...
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2answers
36k views

Calculating the energy supplied by a battery

If you wanted to calculate the energy supplied by a battery in time $t$ you would use $E=VIt$ where $I$ is the current through the battery. If the internal resistance is $r$ we could also use $E=\frac{...
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2answers
676 views

Circuit with three capacitors and a switch [closed]

I have a homework problem where I have a battery connected to a capacitor and a switch that connects the capacitor to 2 others in series/disconnects the circuit from the battery. The question is: ...
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1answer
572 views

Why is the voltage in my battery rising?

While playing with some 9 volt batteries in a series circuit, I noticed that the voltage of the battery as measured by my voltmeter was increasing at a constant rate. After placing a bulb in my ...
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2answers
88 views

Current in circuits and conductivity

I'm really puzzled with a problem for a rather long time and I can't really seem to be able to solve it at all. It has to do with the electrons that move in a circuit. We know that a battery builds ...
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3answers
1k views

Voltmeter- Readings

What would the reading be on this voltmeter? Suppose The battery is $5V$. Would the reading be $5V$? If you see it from the other way, the two ends of the voltmeter are connected by ideal wires; ...
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1answer
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 ...
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3answers
448 views

Does a higher e.m.f give a larger current?

I was told that e.m.f. is the work done on the charge carriers (i.e. electrons in wires or free ions in electrolytes). Does this mean that e.m.f is preportional to current (the rate of flow of charge)...
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1answer
234 views

If a resistance of $0$ ohms and $x$ ohms are in parallel does all current pass through the $0$ resistance? [closed]

If a resistance of $0 \Omega$ and $x$ (and $x>0$) are in parallel does all current pass through the $0$ resistance? For instance in the following circuit: Set variable resistor to o ...
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3answers
1k views

How does connecting batteries in series work?

My question may seem naive so please bear with me. I just began learning about circuits and I am having problem seeing how two or more batteries can be connected in series and how the current flows in ...
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1answer
75 views

Charge generated by battery or wires?

According to emf concept,we say that due to potential difference between electrodes of battery, electrons or charges want to move to opposite electrode. But electrodes are not joined. So they have to ...