Questions tagged [charge]

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

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64 views

Capacitance of 2 angled conducting plates

I have to determine the capacitance of 2 conducting plate (fringe fields are ignored) with a certain area (5m^2 here) with a gap separating them (4mm here). The second plate is inclined at an angle of ...
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2answers
91 views

Magnetic vector potential and displacement current

I'm reviewing some EM theory and I've come across something that doesn't make sense to me. My textbook states that the magnetic vector potential is defined such that \$ \textbf{B}=\nabla\times\textbf{...
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1answer
36 views

Charge transfer in conductors of different metals by touching

when we touch two metallic conductors one is neutral and other has excess of charges, Case 1- Both metals are of copper, then we can calculate actual charges on them at steady state by capacitance ...
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1answer
40 views

Current limiting required for float charge?

I'm trying to make a simple float charge circuit for battery backup of an alarm. The battery specifications state that a voltage of 13.8 is required for float charging and there is no limit on the ...
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1answer
52 views

Battery nominal voltage - can you confirm my understanding?

I am trying to understand why we can simply just calculate the usable energy that a battery has by multiplying the capacity and the nominal voltage. Since the capacity (available electrical charge) ...
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3answers
99 views

Capacitor does not hold charge when switching power

I'm trying to create a power source switch using a relay. This's supposedly will be used for my Raspberry Pi. So what I want to do here is : Create a backup power source with battery that will ...
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4answers
3k views

When do capacitors “decide” to discharge?

I am a beginner electronics designer, but I have never been able to grasp "when a capacitor discharges". What causes a capacitor to discharge? Is there a way to calculate a capacitance value to ...
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1answer
45 views

Car Faraday cage

I have been reading about the Faraday cages in the last couple of days. My learning raised another questions about charge accumulation on a car frame. Air friction can raise the amount of charge on ...
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1answer
42 views

How can this high-side IGBT drive work without exceeding maximum Vg-e

I was reading an article that creates a device that model the I-V curve using on capacitive loads. In the article they using IGBTs to charge and discharge the capacitor. This is the circtuit that ...
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1answer
27 views

Charge sensitive amplifier operation doubt: Same BNC for two purposes. How?

I opened a charge sensitive amplifier (CSA) board which is used in radiation detection. I am trying to figure out how it works. It is totally confusing me that one BNC is used for two signals. How ...
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5answers
151 views

Is the capacity of a capacitor in an RC circuit independent of time? If so why?

Is the capacity c of a capacitor independent of time in an RC circuit? In the notes through which I'm working the following step is made: $$\frac{d}{dt}Q=\frac{d}{dt}(uc)=c\frac{d}{dt}u$$ the ...
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2answers
59 views

Why do I get these voltage offsets when modeling an RC circuit with an AC voltage source?

During one of my homeworks recently, I became interested in modeling an editable graph of an RC circuit charge and current with respect to time. I used the formula that was derived step by step in my ...
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28 views

10mA inverting charge pump

I have limited knowledge of switch caps voltage inverters and charge pumps. I need to generate -2.5V in my system capable of sourcing about 7.5mA. I have MCU and two rails 3.3V and 5V. So far, I ...
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124 views

How to refresh many capacitors quickly

I'm working in an embedded space, where I need to keep voltages on a bunch of capacitors (RC circuits). Currently, I have an EEPROM with some data value for each capacitor. There is 1 DAC that feeds a ...
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1answer
43 views

Energy subtracted from a capacitor for a given voltage drop

I am trying to estimate, from a total energy of a capacitor (which is the output of a charge pump circuitry), how much energy do I have to power up an LED before the voltage goes below a certain ...
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1answer
91 views

Why is there a positive charge at the cathode electrode of a battery in a closed circuit?

Consider a simple circuit that has a resister and a voltaic battery. Here is what (I think) I know to be true: If I draw an arbitrary shape around the battery, the net charge enclosed in that ...
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3answers
109 views

Enough Voltage but No current

I have a query. Suppose, I have a battery. Can some battery have enough voltage but not deliver the required current? How is this possible? My question comes from car batteries but it is not ...
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1answer
41 views

Where in AC the charge gets its energy again?

I'm quite new to electronics. Most of the tutorials I've watched are DC oriented and it's pretty clear that there's a voltage drop across the DC circuit. When current flows through components in DC, ...
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5answers
212 views

Why do charges not lose potential as they travel through the circuit before reaching a resistor?

Voltage is defined as: Given the circuit: Why would potential not drop, from the point differentially away from the positive terminal on the battery, to the point I have labeled. I understand that ...
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17 views

Testing a charge sensitive preamplifier

I have a charge sensitive preamplifier (CSP) that can be used with a photomultiplier tube (PMT) detector. (http://www.cremat.com/CR-Z-PMT.pdf) I am trying to figure out CSP's working. I don't have a ...
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1answer
54 views

Build custom capacitor and measure charge [duplicate]

My goal is to charge small metal ball/cylinder (steel ball - roughly 1 cm in diameter) to the maximum possible capacity. One way to do it is to build a custom capacitor with metal ball being one of ...
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0answers
30 views

Electrostatically charging a capacitor with varying amounts of charge

I'm working on a project that will measure charge, in the nanocoulomb range, of some device powered by some DC power. I'm planning on using a capacitor, a 1 nF, as a means of measuring this charge. ...
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2answers
106 views

Confusion about DC current through conductors

From electrostatics, we know that all the charges reside on the surface of a conductor. We also know that there is no skin effect for DC flow, which implies uniform flow of current throughout the ...
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2answers
83 views

Use of ceramic capacitors in HV system

When I opened the supply board to the detector (Geiger counter,) I got the above circuit. The detector uses a gas-filled tube with a central wire at high voltage to collect the ionization (charge) ...
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0answers
40 views

How much does the gate charge of a MOSFET change over lifetime?

Is the total gate charge of a silicon power MOSFET changing over lifetime, as long as it is used inside its rated operation conditions? I am using a SIHB6N65E (650 V, 600 mOhm) were the datasheet ...
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2answers
74 views

Charge and negative current

Consider the following charge-time graph : If we need to calculate the current in the interval 8 to 12 seconds the current will be negative (since the current is the differentiation of the charge ...
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1answer
30 views

Voltages and charges with regard to ESD

My question is with reference to this question - ESD protection using a capacitor I am unable to grasp the relation between charge, voltage, and capacitance, although I can understand all these terms ...
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271 views

Using Solar Charge Controller with AC Power instead of Panels

I'm working on a project here which needs to have a small SLA backup battery. I have a cheap PWM solar charge controller already and I want to use plugged into an AC power supply (48V DC out) in ...
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113 views

Lithium battery charger and balancer circuit (or IC)

I am working on a project which sould charge and balance 4 to 6 (maybe 8 in future) serial connected lithium cell batteries (~4000 mAh capacity) with about 4A of charge current. First I looked for IC ...
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0answers
30 views

Solving for the current/charge across the elements of this RLC circuit?

I have a circuit which is composed of an inductor (L), capacitor (C), and two identical resistors (R1=R2): This represents an equivalent electrical circuit to a guitar pick or piano hammer as an "...
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1answer
43 views

How to calculate the total charge of a sphere which has a none uniform charge distribution?

If I am given a certain funciton which describes the volume charge density within the sphere with respect to the radius (ρ(r)),how can I calculate the total charge within the sphere.My idea was by ...
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3answers
175 views

Are charge and voltage in a capacitor always directly proportional, regardless of structure?

Capacitance is said to be a constant, and is defined as \$C := \frac{q}{V}\$. I have been unable, however, to find an implementation-independent way to show that charge and voltage are directly ...
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25 views

Charge Distribution on a Microstrip Line

let's consider a microstrip line connected to a voltage source V0 (applied between the strip and GND plane). According to foundation for microwave engineering (collin) book, the surface charge density ...
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2answers
34 views

Energising Electrostatic Charge Into Nylon Ribbons? Is it possible?

Forgive me for how high level this is but this is the goal I'm trying to achieve here: I want to build a device that has dangling ribbons of a material (lets say nylon for now) that can be actuated ...
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25 views

Using a TP4056 with a 08570 Battery

Will a TP4056 (the ones with mini USB and no battery protection) charge a 08570 battery safely? From what I can tell the battery does have built in battery protection but I cannot find much ...
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0answers
30 views

Charging small capacity battery with TP4056

I need to charge a battery which has 20mAh capacity. I have TP4056, is it suitable for this work? There is a formula Ibat=Vprog/Rprog*1200. If i set Rprog to about 100kohm,can i charge a 1C battery ...
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2answers
81 views

Charging a battery without overloading the rest of the circuit

I have a charger circuit (BMS) V1 which charges my LiFePo4 V2 battery, the battery also attaches to a circuit which can take a little more than 3.3v, however if for what ever reason the battery fails ...
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1answer
81 views

Is there a minimum for charging current for lead acid battery?

I've recently bought a 9 V, 3 W solar panel that I wanted to use to make a small project in my balcony, then I bought a 6 V, 4000 mAh sealed lead acid battery, I want the solar panel to always charge ...
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0answers
38 views

Difference between charge-sharing and charge-redistrbution

I've come across these two phenonmenon in several places but I want to know - what's the difference between them in a general two capacitor circuit case (not related to SAR ADCs) Like if I have two ...
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0answers
39 views

Question about charge and discharge of a capacitor

Let's consider the following amplifier: and suppose that a capacitor is connected between the output node and ground. Let's suppose that the inverting terminal becomes much larger than the non-...
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1answer
128 views

Any reasons why my 18650s go very hot when I charge them?

I have some PanasonXX 18650 batteries the grey and the green one I charge them in 2.5A 4.3v but I found that the green battery is very hot after I charge it about an hour later, I don't know the ...
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1answer
88 views

How can a resistor be given a positive and negative characteristic?

This question is not pertaining to a circuit, but to individual parts itself. If for any reason, i want to make a resistor have a positive and negative charge on its either ends, what would be the ...
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1answer
51 views

Solar panel and power bank

I would like to charge a 20,000mAh power bank with a 18V 20W solar panel. The power bank has 8*18650 batteries in parallel. I came out with 3 options. The first one is to use a buck DC-DC converter ...
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6answers
3k views

How can electricity be positive when electrons are negative?

I don't understand how can a for example a battery be positive charged when the electrons are negative charged? I've read that protons are positive but they can't move so are all electricity negative?
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1answer
91 views

Question about a charge injection compensation network for analog switches

I'm studying this kind of CMOS switch: With the switch in Fig. 2.17 in the on state, after a transient, we have Vout=Vin hence the drain to source voltage of M1 goes to zero. The MOS enters the ...
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5answers
172 views

Why does a capacitor charge and discharge?

I know that a capacitor would resist a change in the voltage across its two ends. Assume that the capacitor in the diagram is a fully discharged capacitor( 0v across its ends). Now if I connect this ...
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1answer
53 views

Inrush control circuit

I am analysing the an eval board circuit for a battery charger IC which has the following inrush control circuit. Question 1: I understand that C22 is used to "slow start" Q6 limit inrush current ...
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1answer
74 views

high current UPS ish design

This is my latest attempt to try building a ups ish system for my 3D printer the printer is custom-designed with 5 meters (no, it's not a typo) on each axis. we use MKS Gen v1.1 with custom marlin ...
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6answers
235 views

True or false: A capacitor stores energy for ½ a cycle and gives it up on the other half, the net energy is zero

I'm hoping someone can give me some more information so that I can confidently answer this question. . . True or false: A capacitor stores energy for ½ a cycle and gives it up on the other half, the ...
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1answer
64 views

Voltage Doubler - Charge Pump

The basic understanding of this that I have is that: Assume clock low is 0V, clock high is 3V and Vin is at a fixed 3V. Ignore diode drops Initially Clock is low (0V) and Vin is at 3V (always). ...

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