# Questions tagged [batteries]

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

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### 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 ...
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....
14 views

### 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?
43 views

### 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 ...
19 views

### 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 ...
18 views

### 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 ...
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, $\varepsilon = \Delta V_{-\to+}$, ...
34 views

### Confusion about cells in parallel

I cant understand why cells in parallel will last longer. Could someone please explain?
47 views

### 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?
39 views

### 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 ...
59 views

### 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) ...
36 views

### 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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### 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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### 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 ...
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 ...
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 ...
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 ...
147 views

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 ...
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 ...
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 ...
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 ...
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 ...