Questions tagged [batteries]

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

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20 views

Terminal potential difference of cell [closed]

I was given two cell X and Y of emfs 6V and 4V and internal resistance 2ohm and 8 ohm respectively connected in series with an external resistor of resistance 10 ohm and asked to find terminal ...
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28 views

How do I check to see if a nonrechargeable battery obeys the law of conservation of energy?

For a rechargeable battery, I can show that energy is conserved by Discharging the battery. Measuring the energy required to charge the battery. Measuring the energy I get out from a second discharge....
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In a Lithium Ion battery (during discharge) positive Li Ions flow to the +3.8 volt cathode. Where do they get the energy to climb that 3.8 V hill? [duplicate]

These positive $\text{Li}$ ions are flowing up hill to the cathode during discharge so where is the energy coming from that allows them to get over the hill?
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Conceptual question about capacitors in DC circuits

After a long time when the circuit above has reached steady state and the capacitor can therefore be treated as an open circuit, the voltage at the node directly above the 20 ohm resistor is found by ...
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What would the graph look like if the electrodes were non-equidistant from the dipole?

Hypothetically speaking using the diagram above. If the negative electrode was very far away from this excitable tissue and the positive electrode was right next to it. What would the voltage graph ...
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Why is the cathode of a voltaic battery considered a positive terminal?

I'm a little confused regarding why the cathode electrode of a voltaic battery is denoted as being a positive terminal. Does the positive denote holding a positive charge? Here is what (I think) I ...
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29 views

Why is $\varepsilon=\frac{W_{chemical}}{q}=\Delta V_{-\to+} $ the emf of a battery?

In my book, the electromotive force (emf) of a battery is defined as follows $\varepsilon: = \frac{W_{chemical}}{q}$. The book then states that for an ideal battery, $\varepsilon = \Delta V_{-\to+}$, ...
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3answers
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Confusion about cells in parallel

I cant understand why cells in parallel will last longer. Could someone please explain?
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Find the current in the 23 ohm resistor using Thevenin's theorem [closed]

How should one proceed to find Thevenin's Voltage across the 23 ohm resistor?
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2answers
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Current in a potential divider [closed]

I dont understand why the current in R wont be the same as that in the 50 ohms resistor. Isnt that the rule for series circuits? The emf for the battery is 18 volts.
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How to calculate the battery drain from a LED light knowing it uses 1.5 Ah/month?

My knowledge of physics is basically zero, so I hope this question can be considered on-topic! This thingy connects to the battery of a vehicle (car, motorcycle, scooter etc) and shows the level of ...
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3answers
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Is momentum of electrons conserved when wires form a junction?

Assume constant current flows through the wires. I feel that at the junction, electrons suddenly gain or lose velocity. This is a result of $I=n_e\cdot e\cdot A \cdot v_d$ with $v_d$ (drift velocity) ...
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Energy stored in a capacitor vs Work that the battery does [duplicate]

Say we have a battery at a fixed voltage of $V$ charging a capacitor with capacitance $C$. When the capacitor is fully charged, the energy stored in it will be $\frac{1}{2}QV$, where $V$ is the final ...
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In a simple circuit with only cell and wire, where is the electrical energy lost (what causes potential difference)?

Imagine a simple cell circuit with a nine volts cell. Because of the cell, there is a potential difference of 9V between 2 points on the circuit. Because $$Energy at a point = charge * electric ...
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64 views

RC time constant in parallel circuit [closed]

$R_1 = 50k \Omega $ $ R_2 = 100k \Omega $ $ \mathcal{E} = 10V $ $ C = 10 \mu F $ So I want to find the $\tau$ time constant of this circuit after the switch is closed. The only issue is that ...
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159 views

Simple Kirchoff's Law Problem [closed]

I'm stuck on a fairly simple problem regarding Kirchoff's law, using this diagram: The question asks: What is the current through the $10.0$ V battery? The solution manual says that the answer ...
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How do I find the charge on this capacitor in a complex circuit with multiple batteries? [closed]

! I have the answer to this question, it's 8*10^-6 C. But I have no idea how to get this answer.
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1answer
37 views

Why does the galvanometer read 0 at a certain point?

We are studying potentiometers in class, and our teacher wasn't able to explain why the galvanometer would read 0 at a certain point along the wire. I think I'm not quite understanding how the current ...
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56 views

What does an incompleted variable resistor mean physically?

In the diagram below, the resistor has three terminals I believe. Now in this circuit, my book tells me, that only two terminals are being used (to alter the resistance by sliding the metal contact). ...
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89 views

How is this a parallel circuit?

I understand that here, the current has a choice to flow through one resistor and back to the terminal WITHOUT going through the other. Is this, a parallel circuit? I don't get it. Sorry if this is ...
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In an $RC$ Circuit, when polarity of a battery is reversed, how much energy is dissipated into heat?

https://ibb.co/tPL02dZ In the figure, a $ 20 nF $ capacitor is connected in parallel across a $ 30 nF $ capacitor. There are $2 $ resistors of $10 Ω$ connected in series with the capacitors. A ...
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59 views

Types of circuit

In this image one plate of C1 is at potential of 100v and one plate of C3 is earthened. Which type of circuit is this? If it's open, why would the charge flow?
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Electricity, Voltage, Potential Energy

i wanted ask something about electricity: Suppose we have a circuit:a battery and wires connected to two poles. Also suppose wires have no resistance. Well:When electron goes from negative to positve ...
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1answer
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Why do batteries need a loop to discharge?

I'm an electrical engineer who has been taught transistors and silison and solid state theory and all that. But when I apply the theory to batteries and cathodic protection, my understanding seems to ...
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3answers
75 views

Why does the internal resistance of a rechargeable battery depend upon whether it's charged or discharged?

The following text is from Concepts of Physics by Dr. H.C.Verma, chapter 32, "Electric Current in Conductors", page 199, 19: The internal resistance of an accumulator battery of emf $6\ \mathrm V$ ...
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Electric charge on a capacitor [closed]

What is the electric charge on the capacitor with 3μF? I've tried to apply Kirchhoff voltage law on each mesh, but isn't there any short procedure for it? Many thanks in advance.
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1answer
32 views

Why does potential gradient in a potentiometer wire depend only on driving cell [closed]

The title is pretty much self explanatory.I have done some calculations. I am considering this circuit analogous to a potentiometer, where $E_1$ is my driving cell and $R_1$ and $R_2$ make up the ...
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2answers
103 views

Why is energy absorbed by the battery when the plates of a parallel plate capacitor are pulled apart?

It is said that when the plates of a parallel plate capacitor connected to a battery are pulled apart to increase the separation, energy is absorbed by the battery and no heat is produced during this ...
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64 views

Parallel Batteries

According to Kirchoff Voltage Law we have: $$ V1-IR1-IR2-V2=0 \implies I=\frac{V1-V2}{R}$$ but when testing this i found a 9V battery connected in parallel with a 1.5 Volt battery gives only 2V https:/...
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Using Ohm's law in a loop to find current provided by a voltage source [closed]

I just wanted to know whether you could use ohm's law to find the current in a loop from a voltage source. The circuit in particular is the following: I needed to find V1 using KCL, so I applied KCL ...
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25 views

What causes ${\rm Si}$ to expand when lithiated?

Looking at research into Si-based lithium-ion batteries, the main issue seems to be that the Si increases size by a factor of 4 when lithiated. I'm interested in understanding what actual forces are ...
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How is potential difference greatest when battery is not in a circuit?

I was just studying physics and came across this in the textbook that “A cell produces its highest p.d. when not in a circuit and not supplying current.” Could you please explain this? If the cell is ...
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Parallel plate electrodes dipped into a dielectric fluid [duplicate]

I am trying to solve the problem 50. in a MIT Problem set. The problem is as the picture dipicts. What I am confused is that why the fluid can be pulled up. What kind of force acts on the fluid except ...
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116 views

One side of capacitor plate connected to ground

What is the difference between these two circuits from the point of view of final charge on the capacitor plates? With my understanding, circuit 'A' will quickly accumulate negative charge on the ...
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1answer
46 views

Direction of current when there are 2+ batteries on circuit

By the conventional direction, current points from + to -. But what happens when there are more than one batteries on the circuit,with the battery poles connected to each other with any combination? ...
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4answers
80 views

Work done by battery on a capacitor

Work done by battery on a capacitor is QV/2, where V is the final potential across the capacitor plates an Q is the charge. I know that the Q charge which gets stored on the capacitor comes from the ...
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Physics Circuit Question [closed]

The question asks "How to voltmeter reading will change if the lamp Q is removed". So I was thinking if lamp is removed, then the current flow to the voltmeter will increase thus increasing the ...
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63 views

Parallel vs Series Circuit

If the M lamp breask, why does L get brighter? I tried using the equation, $$V=IR \qquad \qquad \text{with} \qquad \qquad \frac{1}{R_{eq}} = \frac{1}{R_1} + \frac{1}{R_2}$$ but it seems like it ...
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5answers
98 views

How does voltage drop in series connection happen?

The fact that the voltage is the same for two elements connected in parallel seems very clear and intuitive. But when switching to the other related idea, of voltage drop in series connection, I do ...
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1answer
31 views

How to setup a voltage divider to provide a reduced voltage for a lamp

I am learning about voltage dividers. In simple words, a voltage divider is a specific circuit setup where we connect multiple passive elements in series, in order to divide the main voltage into ...
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1answer
112 views

The engineers' style of drawing an electric circuit vs. the physicists' one - a troublesome exercise

I tutor an automation student in physics and math. In particular we deal with all sorts of physical systems with an input $x(t)$ and an output funtion $y(t)$ where the goals is to provide a ...
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69 views

Energy loss through resistors in series

I am trying to understand some A level electricity basics. Unfortunately I stumbled upon a concept that does not seem intuitive to me; this concept goes as follows: for some resistance a charge loses ...
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1answer
38 views

Do the ends of a standard constant voltage supply have a positive and negative electric potential relative to infinity?

This is something that's been on my mind since I was in High School; and today, as a first year physics student I'm still quite unsure. What I'm trying to ask, more specifically, is: I understand ...
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147 views

Paradox in Circuit Theory

Consider the simple case of a battery in series with a resistor, mediated by conducting wire. At steady state, the charge carriers are circulating around the circuit at constant speed through the ...
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4answers
152 views

Induced EMF vs battery EMF

I am bit confused at whether induced emf and battery emf are same in nature differing just in their source. Does a potential gradient exist in case of induced emf as we have when a battery is ...
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3answers
167 views

Why is there no current flowing across the battery

Okay so I solved this question which asked me to calculate the value of R such that there is no current flowing in the galvanometer branch. (THE ANSWER IS 100 ohm) I used the loop rule to write the ...
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2answers
97 views

What happens in a circuit before steady state is achieved?

Okay so consider a circuit with a cell and a resistor. Lets say that the circuit has a switch which is closed at time $t=0$. The following question are based on the state of charges in the circuit ...
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1answer
177 views

What is the source of high pitch noise made by Polaroid instant cameras?

I've been wondering for a long time now, what is the source of that faint high pitch noise that is made by old Polaroid instant cameras. For the reference, the sound at 0:24-0:30 in this video. I ...
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1answer
61 views

Why aren't salt water batteries used to power cars instead of lithium-ion?

I know salt water batteries are less efficient than lithium-ion, but water is safer, can be found anywhere, is cheap and 100% ecological. Even if it doesn't last long, you can refill anywhere. Why can'...
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Question about the potential energy of a charge

If I place a book on a shelf in a gravitational field, the book will of course continuously exert a force on the bookshelf. If I place a small charge above a barrier in an electrostatic field ...

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