# Questions tagged [batteries]

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

402 questions
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### How cell drives electrons to flow in a metal wire?

This was my approach using some facts I'd known- At cathode and anode of a cell reactions take place making positive terminal positively charged and negative terminal negatively charged I.e. there are ...
351 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 ...
183 views

### Trying to understand the electric potential and potential energy

I am trying to understand some facts on electrical potential and potential energy. It is quite confusing in the text to say that the zero potential could be freely chosen for convenience. In that case,...
62 views

### RC circuit series and parallel [closed]

R and 2R are in parallel. 4R and 3R are in parallel. I dont know where to go after calculating the the parallel Rs. Do you become in series? If so, how? It is right after the switch is closed. So ...
35 views

### Powering an electromagnet for a long duration

Looking to power an electromagnet requiring 12 DC volts at 4 Watts, and wondering what size battery I would require to do this for 4 weeks? My maths so far is, and I am not sure this is correct: <...
78 views

### Telling if Capacitors are in Parallel or Series

So C1 and C2 are in series. But if each one is placed in red boxes, they are in parallel? It's confusing going jumping between current, capacitors, and resistance. For me it's kinda confusing ...
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### Amount of energy that can be stored from Faraday flashlight / linear alternator?

You'll have to forgive me if this question is either extremely elementary or does not make sense — I am a civil engineer with little E/M physics background beyond high school education. I am working ...
94 views

### Internal resistance and Instantaneous current?

Okay, this would probably seem a pretty basic doubt but I can't understand this thing. I know that when the current is not flowing in the battery the voltage across the terminals is the emf of the ...
22 views

### Concentric cylinder cell constant

For a concentric cylinder cell (with liquid dielectric), mathematically the equation for the cell constant will always yield a lower value than for the parallel plate case for the same volume of fluid....
34 views

### Work done by battery in moving charge $Q$ in circuit

why work done by a battery in circuit is potential diffrence across plates times charge flown through body. W=Qε(ε is emf of battery) although there are heat and other loses ? and another that my ...
38 views

### What is the field that moves charges in a resistor?

We say a potential difference moves charges in a resistor.. i want to understand it in terms of field. What charge distribution produces a field in the resistor? True, the cell produces a field.. but ...
56 views

### Work done by battery?

Why the work done by a battery is Q*V where V is emf of battery and Q is charge that is made to flow in circuit?please explain detail? explain and write the formulas
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### Why does the potential difference across a type of parallel circuit not act like a potential divider? [closed]

Image credit (Q3) In this attached circuit, when $R_1=0\Omega$, I am failing to understand how the two cells affect the potential difference across the central resistor R3. I understand that ...
243 views

### How to vary the current using batteries?

I am making a door bell as a school assignment. It works by having a solenoid produce a magnetic field which attracts a pice of iron attached on a conductor. when the iron is attracted towards the ...
237 views

### Charge distribution in series combination of capacitors

its a normal series combination of capacitors,only the inner plates are placed differently,one in the beginning and one in the middle,will it not alter the charge distribution ? that is if we will ...
1k views

### Why is there no current between two capacitors connected in series?

I want to ask a question about the figure below. Why the current does not flow from $-Q$ term to $+Q$ term or from a to b since there is a voltage?
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### When the external resistor increases in temperature, why is the calculated value for internal resistance higher?

Say we had a circuit with a cell (with internal resistance)and an external resistor of 10 ohms as shown: The 10 ohm resistor then increases in temperature, leading to an increase in resistance in ...
70 views

### Voltmeter reads zero with two same batteries connected in series [closed]

this is an a level physics question, can someone here please explain why voltmeter reads zero and how changing resistance of variable resistor effects voltmeter reading. The main concept i want to ...
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, ...
67 views

### Does the voltage of the battery change if you use it? [closed]

If you use the battery to charge a capacitor does the voltage of the battery decrease or still the same? Does the voltage of a capacitor decrease if you use it to charge another capacitor?
282 views

### Forces on charges moving through battery

In the attachment, which comes from a text "Introduction to Electrodynamics" by Griffiths. There are two statements: "Within an ideal source of emf (resistenceless battery), the net force on the ...
236 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 ...
37 views

### Kinetic energy and current

When a battery is connected to a resistance circuit, we know that it loses energy because heat is emitted as a result of the collisions between the electrons and stuff, but my question is, is the ...
39 views

### Finding the charge on a capacitor (RC circuit)

I am having trouble finding the charge on the capacitor for $t\rightarrow \infty$ after the switch has been closed at $t=0$. I already know the current $I$. I also have to find out on which sides the ...
68 views

### Resistors parallel to short circuit

I have a trouble solving this problem. (Actually, each resistor is not parallel with the bottom wire since the voltage across each of them is different with that of wire.) In the manual, the bottom ...
916 views

### Voltage and Electric Field in a Circuit

I have a doubt regarding how the electric field acts in a circuit. I have been told that a normal cell creates a uniform electric field, but I find it a bit confusing. Let me explain my doubt with a ...
43 views

### What do we mean by positive terminal and negative terminal?

What do we mean by positive terminal and negative terminal of battery ? What is the electric potential of both positive terminal and negative terminal ? Does positive terminal mean positive electric ...
562 views

### Current from Middle Battery in a Two-looped Circuit

With this question, as with many tutorials of similar questions I’ve found online, my textbook only mentions three currents: $I_1$, which flows through the left loop from and to the 19 V battery, $I_2$...
102 views

### Battery operation, charge and discharge processes misconceptions

I'm trying to elaborate a simple and concise explanation (and conceptually correct) of how a battery charges and discharges, and why we say things like "the charge stored in the battery is x Ah". For ...
104 views

### Would Kirchhoff’s rules not hold in this circuit?

On my E&M test I was given the circuit diagram below and asked to find the charge on the capacitor after a long time or as $t \to \infty$. In class we had used Kirchhoff’s voltage rule on the ...
44 views

### How do electrons gain energy in a cell?

When electrons reach the positive terminal, how does the cell do work on them? I’ve read in a book that states voltage is literally the push that the cell exerts on electrons, which thus does work on ...
28 views

### Calculating energy capacity of a battery

I understand that you can easily calculate the energy capacity of a battery simply by multiplying the mAh rating by the Voltage. However, my question is how do the manufacturers calculate the mAh ...
120 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 ...
145 views

### Stacking batteries and electron flow

About Fuel Cells and Batteries: I understand the analogue with increased water height as two cells (battery or fuel) are connected in series. However if we for instance have two batteries contected in ...
30 views

### How to choose the method of circuit analysis?

I was just doing some revision, and I was wondering how to figure out which method to use for solving a given circuit? I tried using mesh analysis on the attached circuit but I got it completely wrong....
43 views

### Does Stopping Voltage actually produce 0 photocurrent?

The stopping voltage is the voltage applied across the photoelectric plates to measure the maximum KE of ejected electrons. This is as the electric field will apply a force against the velocity of the ...
24 views

### Question about amp-hour and batteries in series

I am a little confused about this wiring batteries in series and parallel and the effect of this on total time that these batteries can last(I suppose this is called amp-hour, correct me if I'm wrong) ...
78 views

### Different batteries in a parallel circuit

I have come across this question in my physics textbook. Two batteries are connected in parallel to a resistor (see the above image). The first battery generates $U1 = 9V$ of voltage and its internal ...
85 views

### RC circuit discharge while being connected to a battery?

I am facing a conceptual problem in analyzing the following situation which was part of a physics exam; A series RC circuit with $R = 200k \Omega$ and $C = 10 \mu F$ is connected to a 5V battery and ...
69 views

### What happens when a battery is dead?

While studying circuits I am having a question that when we say a battery is dead.Do we mean that the voltage difference between the ends has become zero?If no,then what actually happens?
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 ...
70 views

### Practical usage of batteries connected in parallel

Is there any practical usage in real devices for connecting batteries in parallel? Or is it more a theoretical construct? It seems to me that only batteries in series are used nowdays.
69 views

### Can anyone tell me why the answer to this question is D? [closed]

I think the current will go through earth wire but my physics teacher told us the current will continue to flow through the circuit.
34 views

### Empty and fresh battery in series

If you have 2 (e.g. 1.5V) batteries in series and one is dead/empty, what is the reason why a device is not working? Lack of voltage (1.5 + 0 is simply not enough for the device to operate)? From my ...
54 views

### Why did a 12V battery affect my motor more than two 9v batteries in series?

In class, we made a coil of wire and used it to make a simple electric motor with a magnet. I put two square 9v batteries in series for a total of 18v to power the motor. I then used a larger 12v ...
71 views

### Doubt while simulating electric circuits

Today, I was simulating DC electric circuits just for knowledge and fun using PhET interactive simulations. But I'm having trouble understanding these circuits which I made. I think that both these ...
82 views

### The importance and the role of a switch in an electrical circuit

There is this simple test: Three identical bulbs are connected in the circuit illustrated in the figure. When switch $S$ is closed: a] The brightness of $A$ and $B$ remains the same, while $C$ goes ...
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### For a real battery, why is two identical bulbs in parrallel slightly more dim than just one in series

Image for reference: \begin{align} &r = 0.8\,\Omega\\ &\mathscr{E} = 1.5\,\mathrm V\\ &A = B = 6\,\Omega. \end{align} The current when the switch is open, the only other resistor is ...