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Questions tagged [batteries]

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

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168 views

Internal resistance and a resistor as a potential divider

Based on the fact that batteries have some kind of internal resistance, if I had a circuit that consisted of a battery and a resistor of some kind would they act like a potential (voltage) divider? ...
116 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 ...
330 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 ...
32 views

Voltage Change Across a Resistor/Circuit

Say you have a 9 volt battery, and you connect the two ends of the battery with a wire to form a circuit with no resistor. If you measure the potential difference between the two ends of the battery, ...
36 views

What power density could a cell phone battery achieve, and how?

Current cell phones have batteries reaching about 3500mAh capacity, and I believe Lithium-Ion technology is rated at around 100Wh/kg (?) Is there a theoretical limit to how much power could be stored ...
58 views

What if I keep holding a household battery?

I have a question in my mind. What if I keep holding a Duracell(1.5V Battery) touching both the terminals with my fingertips? Will the circuit be completed and the battery drain? Or will it have no ...
60 views

Voltage measurement

Why does multimeter show 0 V ?
24 views

What will be the equivalent resistance of this circuit? [closed]

What will be it's equivalent resistance
138 views

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 ...
17 views

Meaning of negative emf in the context of Kirchhoff’s Voltage Law

I’m wondering what it means when the emf of a battery is calculated to be a negative value through Kirchhoff’s Voltage Law. This is the problem: As you can see, we’re given the currents, and we can ...
43 views

Why current flows in an inductor?

If during self-induction the inductor produces a current in opposite direction of that of battery in order to resist the change of current through it then how could the current after some reasonable ...
2k views

Why is the potential drop zero across a wire of zero resistance? [duplicate]

Okay, even if the wire has zero resistance, then charges are being transferred in the direction of electric field, which means there must be a potential drop according to the distance travelled by the ...
620 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, $I_2$...
280 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 ...
19 views

Potential and work across capacitor-battery circuit

Suppose, we have a simple capacitor/battery setup like that shown below. The battery is used to charge up the capacitor. After the capacitor is charged, there will be equilibrium, the field of the ...
3k views

Emf of a Cell in an Open Circuit

Consider a cell having terminal voltage $V'$ and EMF, $V$ having internal resistance, $r$ and current, $I$ flows through the circuit in which an external resistance, $R$ is connected. Potential drop ...
280 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 ...
126 views

Parallel voltage source concept

I am having doubt understanding this: If two voltage sources V1 and V2 are connected in parallel with different voltages like 2v and 3v is it possible or the scenario is wrong. An example is this ...
14 views

Is Lithium Plating possible at the cathode, too?

When talking about the Failure Mode 'Lithium Plating' in Lithium Ion batteries, in literature it is just described at the anode and I could not find answers to why it is not happening at the cathode, ...
163 views

Why aren't gravity batteries everywhere? [closed]

The problem of energy storage, especially with regard to renewables, remains unsolved. Or at least there do not seem to be any popular solutions. Why not gravity batteries? I love the idea, and ...
59 views

Why brushless DC (BLDC) motors usually have low voltage and high currents? [closed]

I am not an engineer, and neither familiar with motors, so bear with me. :) Thorough explanations needed. :) The question is, why brushless DC motors intended for RC models and possibly paragliders ...
58 views

A simple circuit problem / maximum power [closed]

Let us solve the first part for $R_{L}$. I used Thevenin to make its equivalent circuit. We get $R_{Th}$ or $R_{eq}=110/3=36.67$, so for maximum power transfer it must be equal to $R_{L}$. I can't ...
69 views

Creation of electric field inside a conductor

My book says that as soon as the two ends of a conducting wire touches the two terminals of a battery, it generates an electric field inside the conductor. Why?
184 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 ...
510 views

Connecting a charged capacitor to an uncharged capacitor

I was attending a lecture about capacitors and something confused me. If I charge a capacitor using a DC supply, the capacitor will gain charge $Q_0$. Now, if I discharged it along an uncharged ...
1k 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 ...
146 views

Why are(n’t) rechargeable batteries damaged by partial charging?

Originally asked in ElectricalEngineering.SE, but I was told Physics.SE might be a better place to ask. Over the years, I've come across websites and people with different opinions on the "correct" ...
360 views

What happens when electrons reach the battery?

We have a capacitor which is connected to a voltage source. The top plate of the capacitor is connected to the positive terminal of the source. Therefore, electrons go from the top plate to the ...
154 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 ...
38 views

can there be a circuit that changes its input source after a certain limit of voltage is hit? [closed]

I have only recently started learning about circuit components and only know about common components such as a capacitor and a little about diodes, so excuse if im not able to understand common terms ...
62 views

Would we need a battery if there was no resistance?

I'm struggling to wrap my head around this idea. Imagine that we have a wire with no resistance ($R=0$). According to Ohm's law $V=IR$, the voltage drop ($V$) between any two points would be 0, and ...
39 views

Potentiometer's working

I know that in a closed circuit with multiple batteries, current is provided by the battery which has the maximum voltage. Let's suppose that $E \gt V$. Now, the voltage $V_b$ at point $b$ will ...
61 views

Conflicting models about how energy transferred in an electric circuit [duplicate]

I've been studying DC circuits recently, but I've run into some confusion concerning how batteries deliver energy to circuit elements. From what I've read online, it seems that energy in circuits ...
16 views

Field forces in a battery

Does a battery take time to reach its maximum voltage because it will take time for the field forces to build up since the electrodes are initially uncharged?
56k views

What is the difference between a battery and a charged capacitor?

What is the difference between a battery and a charged capacitor? I can see lot of similarities between capacitor and battery. In both these charges are separated and When not connected in a circuit ...
13 views

Difference between Capacitor and a battery [duplicate]

Capacitor stores electric charge and battery also stores electric charge. SO whats the difference between them?
130 views

Does current flow when you connect a battery to earth?

Let's say that the earth has 0V and everything is ideal, does current still flow and why?
197 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,...
45 views

Forces inside battery

The title itself seems silly to me but here is this question, A constant electric force of $8\ \text{N}$ acts in the direction shown and constant non electric force of $10\ \text{N}$ acts rightward, ...
75 views

Energy Density is expressed in Liters, Liters of What?

When looking at energy density of batteries it is often expressed as Wh/L. For instance, Wikipedia says Lithium Ion batteries have a density of 250–693 W·h/L. Liters is supposed to express the volume ...
57 views

How do surfaces charges accumulate?

When a voltage source is applied across an ideal wire, do the push of electric field of battery source causes the accumulation of charges on the surface of wire or the capacitance of wire causes it? ...
33 views

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 ...
494 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 ...
68 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 ...
37 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: <...
93 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 ...
108 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 ...
32 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....