# Questions tagged [batteries]

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

394 questions
2answers
53 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
5answers
79 views

### Why does the potential difference across a type of parallel circuit not act like a potential divider?

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 ...
2answers
231 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 ...
1answer
224 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 ...
4answers
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?
1answer
26 views

### 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 ...
3answers
66 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 ...
4answers
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, ...
1answer
33 views

### Voltage in a potential divider circuit [closed]

I am considering the following circuit: I need to find the voltage across the $30$ Ohm resistor when the variable resistor's contact is halfway between X and Y, such that its resistance is $5$ Ohms. ...
1answer
64 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?
1answer
274 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 ...
3answers
231 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 ...
0answers
24 views

### Current through lamp when an extra component is added in the circuit

I cant figure out part ii. (the lamp is the X) I calculated the total current in the circuit, which increased to 10.24A. thus, the voltage drop increased and voltage across the lamp decreased to 11....
2answers
36 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 ...
4answers
37 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 ...
1answer
63 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 ...
2answers
818 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 ...
1answer
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 ...
3answers
548 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, $I_2$...
1answer
95 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 ...
1answer
99 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 ...
1answer
39 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 ...
0answers
24 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 ...
1answer
114 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 ...
2answers
144 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 ...
0answers
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....
1answer
42 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 ...
0answers
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) ...
1answer
69 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 ...
3answers
83 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 ...
2answers
53 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?
5answers
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 ...
3answers
67 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.
3answers
67 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.
2answers
33 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 ...
2answers
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 ...
1answer
68 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 ...
2answers
62 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 ...
2answers
38 views

### 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 ...
1answer
29 views

### Why do we subtract the voltage of the resistor from the emf voltage to find the terminal voltage?

I attached an image of a question from homework. I calculated the current in step 1) and then I calculated the voltage of the resistor. But why do I need to subtract that voltage from the emf voltage ...
1answer
29 views

### Direct current electric circuit

Why when I reverse one of the three batteries in a torch light, the bulb does not light up? The three batteries (one of them is reversed) and the bulb suppose to form a closed loop. According to ...
1answer
19 views

### Question about electrochemical reaction in fuel cell

The electrochemical reaction on the anode side of a fuel cell can be expressed as hydrogen split into hydrogen protons and electrons. I'm doing some research about the electrochemical reaction in a ...
2answers
35 views

### Voltage when lamp burns out [closed]

In the question below, shouldn't the voltmeter read zero V because the circuit is broken and there is no current flowing? (the answer in the text is 12v)
3answers
80 views

### Why doesn't the flow electrons occur in a broken circuit?

Take a battery and connect a small led bulb across it with the help of two wires. The bulb will glow, but if I cut a small piece of wire from any part of the connecting wires,the circuit will not work ...
1answer
35 views

### Intuition behind swapping the known and unknown resistance in a slide wire meter bridge

Today I was learning about wheatstones and balanced meter bridges. But while learning about the sources of error while working with the meter bridge (measuring unknown resistance), I couldn't ...
2answers
118 views

### How do voltmeters measure work done over a component?

In my physics class, we were shown the picture below to measure the current and potential difference through a component. We were told that the resistance of the ammeter is as low as possible, and the ...
1answer
998 views

### Why would 4 batteries in a device not drain equally? [closed]

I noticed a motion sensor light was weak so I assumed the batteries were dying and removed them. To make sure I was right, I tested the 4 D alkaline batteries. One was completely dead. One was on the ...
2answers
49 views

### Power in a simple electrical circuit [closed]

In this picture, as we know power due to heating of the resistance is $V^2/R$ . Now, if we add a parallel resistance to the circuit, the power dissipated through this resistor is also $V^2/R$ ...
6answers
2k views

### Does the resistance of the voltmeter affect the behavior of this circuit?

I have this setup. It consists of a battery of no internal resistance with voltage $V$ and a resistor with resistance $R$. It also consists of a voltmeter of some (not so large) resistance as good ...
1answer
162 views

### Li-ion Battery charging

Why are constant current mode and constant voltage mode needed when charging Li-ion batteries? Why do we apply saturation charge even after the cell voltage reaches 4.2V? What exactly is 'I-sense' in ...