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Questions tagged [charge]

A fundamental physical property held by various particles, most notably electrons

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0answers
54 views

A conductive ball connected to a capacitor

I am not asking for a task solution, but rather how to solve a problem. Say I have a ball of radius R, charged to a voltage of U (relative to the ground). I also have a flat capacitor with a side ...
7
votes
3answers
2k views

If a lithium cell is said to have a capacity of 20 Ah, does that mean all 20 Ah can be used?

Toshiba's SCiB 20 Ah Lithium titanate cell is said to have a nominal capacity of 20 Ah. The cutoff voltages are 1.5 V and 2.7 V. Does this mean that all 20 Ah of charge exist between those two cutoff ...
0
votes
1answer
45 views

Battery charging rate for 3.7 v [closed]

Hello, we have a project for electrical engineering. We charge a 3.7 volt battery with solar energy as the project, but we do not know if the battery is charging or not. How do we know the charge rate ...
0
votes
0answers
40 views

Connect backup battery pack with BMS HX-3S-01

I want to connect a LiPo 11.1V battery pack with HX-3S-01 BMS board to my circuit. I found some other boards with separate power input and and output. But this one has only one (Charge/Discharge P+-)....
2
votes
1answer
75 views

Charge Injection Confusion

I'm having some trouble understanding the effect that charge injection has on capacitors - more specifically, when there is unequal charge on a capacitor. Consider the following circuit: My ...
1
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0answers
22 views

Responsible Battery Reserve Capacity and Low voltage?

It's been asked here, but looking for clarity. How bad is it to undervoltage a 12-volt lead-acid battery? SLI automotive starter batteries list RC (reserve capacity), but I think this a usable ...
0
votes
1answer
24 views

Charge Measurement for Piezoelectric Sensor

I want to measure the charge displaced by a force acting on a piezoelectric sensor. The problem is I don't know the sensor so I have no idea how big the current generated by the sensor may be nor what ...
0
votes
4answers
81 views

Supercapacitor backup circuit - why seperate charge and discharge path?

I am learning about super capacitors in a backup power application. I see a lot of examples using diode networks or FETs to separate the charge and discharge paths. Why is there so much effort put ...
11
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3answers
284 views

How much do lithium polymer batteries expand in volume?

I'm designing a device with a small lithium polymer battery (4x12x30 mm, 120 mA-h). Looks like this: I've heard that there is a rule of thumb that the space left for the battery in a case should be ...
0
votes
2answers
75 views

How to charge two 18650s in series without a middle connection?

I have a battery pack of 2 18650 cells in series, so it is possible for me to charge it without connecting anything to the central 3.7v potential point as many answers mention? The battery in question ...
1
vote
2answers
41 views

Something wrong with open USB circuit, electrostatic problem

I faced a strange problem with the following circuit. I'm using some buck converters and an Arduino. The buck converter (Vout = 5.25v) is for a USB charger (up to 2 Amps). Well, I think the circuit ...
0
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0answers
51 views

If we're wearing a metal watch, do we get an electric shock on our wrist when we're charged and touch a conductor?

Or if the conductor itself is charged. As the charge would flow to/from the watch, assuming I'm insulated from the ground with rubber soles, or standing on glass.
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1answer
67 views

How does a camera pixel accumulate charge (colour)?

I refer to the Wikipedia entry for a CMOS camera sensor's individual pixel. There is a schematic like so:- and a statement that:- The read-out transistor, Msf, acts as a buffer (specifically, a ...
0
votes
4answers
194 views

What happens to the energy stored in a short-circuited capacitor?

Suppose we have an ideal capacitor with a certain voltage between its plates. We connect the two plates using an ideal (lossless) wire, so the capacitor discharges. Where has the energy having been ...
3
votes
2answers
410 views

A question about electrons, charges and current

Let's talk about DC, a very simple circuit: a light bulb and a battery. Some authors say that electrons move from negative to positive and current from positive from negative. I always thought ...
1
vote
1answer
30 views

What determines the direction and cause of electric field exerted on test charges?

-I understand when there is an on-going electric field, if it is produced by a positive charge, the direction of electric field is away from it etc. And, if we get a +ve test charge, it repels it, and ...
0
votes
3answers
92 views

Electric field strength from AC conducting wire in form of a loop along z-axis?

Let's say I want to calculate the electric field strength from an AC conducting wire, with a certain frequency and current. The wire is in the form av a loop. I want to calculate the E-field along the ...
0
votes
3answers
179 views

Confusion over the power wires of USB (GND and +5v)

I'm converting a battery powered device to be powered off a USB connection. I think I have everything figured out except one thing. I understand there is a GND wire inside the USB cable for power, ...
1
vote
3answers
69 views

Single Cell Battery Protection ICs

I'm designing a product that will be powered by a single 18650 cell. Specifically, I am basing my numbers off this cell in particular: Samsung INR18650-25R It has a typical full voltage of 4.2V ...
5
votes
1answer
384 views

Measuring MOSFET input capacitance?

Am I calculating total input capacitance or gate capacitance or none of the above? And are my calculations even correct to begin with. The point of this is that I want to know what gate capacitance im ...
0
votes
1answer
97 views

Why does capacitor never fully discharge in this circuit?

I've found in the following circuit, when the value of RPD is very high (say 10MΩ), sometimes the capacitor actually never fully discharges and the mosfet stays partially on. The LED dims but never ...
3
votes
0answers
106 views

Parallel connection of old and new gel batteries

I have a battery system shown in the picture, 6 parallel branches of 4 batteries connected in series. The first 3 consist of old batteries which are 2 years old, the fourth branch consists of 1.5 ...
0
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0answers
51 views

Ultracapacitor doesn't charge

I am concerned about an ultracapacitor (2.7v, 3000F) that I received today. I set my power supply to 2.5v with a current limit of 1A, then connected a diode to the positive lead such that current ...
1
vote
2answers
61 views

Calculating charge entered into a circuit element for a given time

Looking at p 1.2-4 in Introduction to Electric Circuits by Dorf (See top of p16) I don't understand why the charge for 4 < t < 8 is 8- t. The current for that time is given as -1. So ...
0
votes
1answer
29 views

GaAs and GaN as low temperature carriers in transistor

I've been looking at HEMT to use at low temperatures. GaAs and GaN seem to be discussed often in the context of low temperature amplification. My questions are twofold. To be suitable for low ...
1
vote
2answers
45 views

Measuring floating gate potential with minimal leakage current

I am working on a sensing device where the voltage of a floating node is dependent on the quantity to be sensed, as well as the net charge stored in the node. I would like the device to be only ...
0
votes
1answer
54 views

Trying to solve a RL circuit by hand but simulator calculates a value I do not understand

I have this circuit. V3 is just a trigger to close the switch, just ignore it. The switch is open for a long time. So, the left part of the circuit is working for a long time and the inductor is ...
0
votes
3answers
219 views

Why does current have to return to its source in a circuit?

As far as I know there should be a current when a high potential point is connected to a low potential point, but apparently that is not true. I understand that a circuit must be closed in order for ...
0
votes
3answers
79 views

Average Current vs Arithmetic Average

I am just starting to learn the theory of electronics. Coming from a probability and statistics background I have a very deeply ingrained idea of the term average. The average to me is the ...
-1
votes
3answers
163 views

Voltage drop solution?

i just wanna start by saying i appreciate any help at all and am grateful for this forum! Also, the only electrical knowledge i have are that of self experimentation, no education except reading ...
0
votes
1answer
34 views

What kind of setup can take portable solar USB power & charge a AA battery charger that is usually designed to plug into a wall? [closed]

I have a portable solar panel that generates 21w of power, seen here: enter link description here . It has a USB connection wired into it that will accept a USB cord to charge small devices via USB. ...
0
votes
1answer
76 views

Slow-start lead-acid charge - good or bad?

I have a 300Ah battery which is near-dead (Abused in the past, around 5 years old) and want to replace it with 4-6 new 100Ah. The current method of charging is with a 30A MPPT solar controller. As ...
0
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2answers
181 views

Importance of the constant voltage charging of li-ion

Hello everyone is it necessary to have the constant voltage (CV) process when charging 18650 li-ion batteries? What happen if I usually skip the CV? Does the li-ion battery got memory? I know the ...
-1
votes
1answer
70 views

Input power vs charge curve (battery charging) [closed]

I want to know when charging a battery whether the charger reduces its current input as the battery reaches 80 percent charge, because it takes longer to charge the battery due to the charge curve. ...
-2
votes
1answer
55 views

How can I find charge from output signal of the Photo Mulitipier Tube?

Here I have a scintillator detector with PMT, It give a signal when a particle passing through it. I need to find the total charge from the signal. How can I find charge from the signal?
0
votes
1answer
99 views

Can throwing charged capacitors cause magnetic fields?

Since current is just buckets of charge passing through a point in space per unit time, and a capacitor is a literal bucket of charge, I had some questions in mind. Is throwing a charged capacitor ...
0
votes
1answer
86 views

Power loss in an RC circuit with very low resistance [closed]

I read at some point that an RC circuit with extremely low resistance might end up not being more efficient than one with higher resistance because the voltage change will be so fast that the ...
0
votes
2answers
167 views

Can a capacitor charge and discharge at the same time?

Is it possible to use the stored energy while the capacitor is being charged? In other words, use a capacitor almost as a conductor? My gut says the answer is probably no (and my own experiments so ...
19
votes
4answers
8k views

Do you need high voltage or current to produce a spark?

An electric spark can be formed when there is high potential energy between two conductors, right? My question is can a spark be formed with high current and low voltage or only vice-versa?
0
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1answer
63 views

Charging Capacitor

Is it possible to use the leakage current from many capacitors to recharge another capacitor or decrease the leakage current in another capacitor?
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1answer
792 views

MOSFET DRIVER- HIGH side vs LOW side

I am trying to understand mosfet drivers in general, no specific part. And I am encountering low side and high side drivers. My question is that if for example: I have a N channel mosfet as a high ...
1
vote
2answers
94 views

Are the anodes and cathodes in a vacuum tube truly charged?

Are the anodes and cathodes in a vacuum tube truly charged? Can I treat them like any other charged object? also how can I calculate the charge? How would I calculate the alternating charge if it's ac?...
1
vote
1answer
101 views

Why doesn't this capacitor voltage rise when the current does flow into it

I use a capacitor and a resistor to be a battery,the simulation show me the current does flow into it(charge it).The reason that i believe the current does flow into the capacitor is because that the ...
1
vote
0answers
84 views

Charging 3.7V battery from 300W+ generator

I am doing a project involving a bike generator of 500W. All of my previous projects were small LiPo battery powered devices so I want to double check certain aspects of this relatively high power ...
0
votes
3answers
3k views

Jump start car with AGM battery

I jump started a car with an AGM battery and later discovered that the 30A fuse connected to its positive terminal had blown. I suspect that this occurred while performing the jump start. How many ...
0
votes
0answers
147 views

MPPT charge control Project - LT3652

I am doing a Solar powered power bank as my dissertation project. It's based on LT3652 charge control, a Lithium-Ion battery (4500mAh) and 2 boost converters (3.3-5V and 3.3-12V). I am using a 21W, ...
0
votes
2answers
54 views

How can I increase the number of USB outputs of a powerbank which only has one output? [closed]

I'm talking about outputs which we use to charge our devices with. Would using USB male to two USB female cord be a bad idea?
0
votes
1answer
133 views

Misunderstanding from the author saying,about the current flowing path

The author show the working process of this schematic 1.The proposed system waits until the PZT device stores the energy vibrations produce during the positive half of vibration period \$T_{VIB}\$ ...
2
votes
2answers
146 views

What power supply current rating can replace 6 1.5 V C batteries?

I have a more specific question than this one. As I understand it, different 1.5 V batteries are distinguished by "capacity" (AAA < AA < C < D), measured in mAh (milliamp-hours(?), which is ...
0
votes
1answer
91 views

Not sure if this capacitor will blow up [closed]

so i have just bought a fan controller(silverstone cpf04) and it is rated with 2200μF and i am planning to connect 7 fans to it. (NF-F12)4 fans are each rated with 12v operating voltage 3.6w input ...