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Questions tagged [charge]

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

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charge capacitor in two phases

i want to charge two 25F Supercaps (in series) in two stages: while their total voltage is under 5v, i want to charge them slowly via a resistor R3 of around 100 Ohm. After they reach the desired ...
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40 views

Finding the voltage across a inductor in a charged RLC-circuit

Well, I've the following circuit: simulate this circuit – Schematic created using CircuitLab In the circuit I want to find the voltage \$\text{V}_{\text{Y}_1}\left(t\right)\$ as a function ...
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35 views

phone charger residual electric flow

Not actually sure if this is too simple a question for this exchange. Just now I picked up my phone charger and unplugged it to move somewhere and plugged my phone in to the recently unplugged (from ...
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45 views

Removing a charged coil from circuit

I have a question: If I charge a capacitor through a resistor and remove it from the circuit, the capacitor will be charged for a certain amount of time (eventually the voltage across the capacitor ...
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31 views

What does this ɣ constant relate to in the carrier motion of BJT

What does the constant ɣ represent in the following carrier motion of an PNP transistor? So I see three components for the base current. 1) According to the illustration I can see that some of the ...
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56 views

How to calculate gate charge time for a mosfet?

I am designing the circuit shown above using mosfet NDS355AN. MCU is 5 V. However, I have become stuck as I am unsure of how to calculate the gate charge time of the mosfet. Hence what is the formula ...
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33 views

Simplified eqn for inductor charge for short timeframe?

In a worked solution my professor has given me it says: I(load) = Io(1-e^(t/time constant)) and I(load) = Io * (t/time constant) (for a short time period) I don't understand how the second line can ...
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54 views

Calculating charge given current and capacitance over time

I it possible to calculate the charge on a capacitor when only having the current, time and capacitance value? I tried using this formula to first calculate the voltage and from there the charge. ...
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51 views

How to switch between charge and discharge?

I want to make my rpi 3 portable with adding a rechargeable battery pack to it. I have 6 Li-ION batteries that are packed together in 2 series rows of 3 batteries in parallel(each battery is a 3.7 ...
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114 views

Battery operation, charge and discharge processes misconceptions

I'm trying to elaborate a simple 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 now, I have ...
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41 views

Transfer charge from a battery to another battery storage

I am conducting a feasibility study and one of the features of our innovation is that the "charge" that has been stored in our "Li-Po battery" can be transfer to another "battery storage" I would ...
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34 views

Optimal Grounding for a PVC Dust Collection System?

It is common in woodworking (A hobby of mine) to make a dust collection system (Basically a tube hooked up to a vacuum to carry away dust created from automatic woodworking tools) out of PVC. We'll ...
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How to determine the steady state voltage across two capacitors in parallel

Say we have two capacitors C1 and C2, initially isolated from each other and each having an initial voltage Vc1 and Vc2 respectively, where Vc1>Vc2. When suddenly connected to each other in parallel, ...
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58 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 ...
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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 ...
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89 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+-)....
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89 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 ...
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25 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 ...
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27 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 ...
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4answers
109 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 ...
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3answers
332 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 ...
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2answers
100 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 ...
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46 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 ...
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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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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 ...
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205 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 ...
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2answers
414 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 ...
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1answer
31 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 ...
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3answers
93 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 ...
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3answers
261 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, ...
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3answers
79 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 ...
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1answer
529 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 ...
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108 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 ...
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145 views

Parallel connection of old and new gel batteries [closed]

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-...
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52 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 ...
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2answers
74 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 ...
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1answer
32 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 ...
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2answers
47 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 ...
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1answer
55 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 ...
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3answers
306 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 ...
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3answers
83 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 ...
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3answers
184 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 ...
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1answer
40 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. ...
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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 ...
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2answers
249 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 ...
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1answer
78 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. ...
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1answer
57 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?
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102 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 ...
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1answer
111 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 ...
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2answers
249 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 ...