# Tagged Questions

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

578 views

### Understanding voltage and current

While reading "Electronics for dummies" went through the following block and I realised that I have some uncleared concepts about electricity: Electrostatic discharge involves very high voltages ...
1k views

### How to use a capacitive touch screen without a human hand

I'm a programmer, and I usually hang out over on stack overflow, but I have a electricity question. I'm trying to interact with an APP on my phone by indirectly touching the the screen. Modern ...
188 views

### Discharge and charge rates of a capacitor - Comparing Energy Movements

This is a really simple question. But I'm seeing some confusing behavior in an experiment I'm trying to make sense of. So I'm trying to see if my understanding of theory is wrong. Wikipedia says: ...
2k views

### Why is the Anode positive if Anions are negative…?

When I was younger I learned in Chemistry class that Anions were negatively charged and Cations were positively charged (Fun fact: I memorized this because anion sounds like onion which makes you cry ...
185 views

### Why DC voltages in series do sum (or subtract, according to polarity)?

This is a newbie question. It is clear that if you put two (or more) DC voltage sources in series like this: simulate this circuit – Schematic created using CircuitLab And you measure ...
624 views

### Do electrons actually flow when a voltage is applied?

It's said in books that a circuit is a closed path and thus that electrons come back to the source. If that's the case, what would happen when there were an earth fault in a circuit? How would the ...
584 views

### Charging 35V 470uf capacitor with coin cell

I want to charge a 50V 470uF capacitor up to 35V with the smallest battery possible. Can a coin cell do this 3000 times? Possibly a 2450 or 2477 coin cell? Also, can the capacitor be fully charged ...
354 views

### Voltage used to charge a UPS-Inverter and its usage

I'm new to this area and know very little about electrons and how electrical components work. I'm always curious about Inverter/UPS usage. I'm from India and we have a inverter at home. It is ...
553 views

### Questions about capacitors in DC

1.Does the current flow through the capacitor when (a) it's not charged, (b) it's partially charged, (c) it's fully charged ? How does the flow changes in time (ex.: exponentially, logarithmically, ...
414 views

### Generating Strong Electric Fields

What is the best way of generating strong, steady, electric fields (E) using the tools and voltages available to the home hobbyist? Is it better to using electrostatic sources like a Van de Graaff ...
426 views

### 220V 0.2A converted to 12V 5A, where are the missing amperes?

I have an AC adapter at home that reads (roughly) the following: uses 220-240v AC 50Hz at 0.2A produces 12V DC at 5A I'm a little surprised that it uses 0.2 amps and produces upto 5. Here's what ...
353 views

### How is saltwater able to conduct electric charge between two wires?

Say I put some wires in a container filled with saltwater, but the wires do not touch, and I connect these wires to a battery: simulate this circuit – Schematic created using CircuitLab ...
138 views

### Need chargeable momentary 15 watt regulated voltage source

I'm working on a RF telemetry side-project that requires an amplifier IC to be run for about 5 seconds bursts between charges. The system is portable and runs off of a 3.3V battery that can supply ...
98 views

### From pulse height to number of electrons

Assume that there is a pulse on a scope with $100\;mV$ height, as shown in picture This pulse is coming from a photomultiplier tube. How to determine the number of electrons from which this pulse ...
207 views

### Calculate Charge time of capacitor with current limiting power supply

If I have a 10VDC supply current limited to 1AMP to charge a capacitor through a 1 ohm resistor, what will happen and how long does it take to charge? I need a capacitor that can "eat" this power for ...
265 views

### Why does conventional electricity flow out of + in a battery, but out of - in components?

It seems like when electricity flows out of + in a battery it should be attracted by a - end of a component, but it's not like that. Why?
732 views

### Low current battery monitoring

I want to run a micro-controller from a 1S lipo through a 3V linear regulator. I need to measure the battery voltage however. The problem with using a voltage divider is that it would drain the ...
130 views

### how to charge a steel ball

I have a 2 mm radius steel ball and I want to charge it in a 0.025 Coulomb charge. Can I do that domestically or the charge is too high? And how can I do that assuming I don't have another conductive ...
286 views

### charging and discharging capacitors

I'm wondering if it's possible to charge say a capacitor with a stepper motor (~12V DC after rectifying), which when it reaches its maximum capacity discharges. I'd like the discharged power to ...
192 views

### Battery charge indicator LEDs

Many laptop batteries have a button on the bottom that will light up 1-4 LEDs to indicate how much power is remaining. I'd love to build something like that into my own device, which is powered by 2 ...
581 views

### How to impart a charge on dust particles?

I am planning on building a simple electrostatic air filter, from scratch. From what I understand, the dust in the air is given a charge as it flows through an inlet section and is collected by mesh ...
228 views

### High input voltage charge pump

Related to my last question, I decided to go with a step-down charge pump to convert 5V to 35V down to 3.3V at 10mA, due to the smaller required component size. However, I can't find a single charge ...
304 views

### MAX1555 Alternatives

As you know, the MAX1555 is a popular single cell lithium polymer charger. It can take USB power directly, restricting the charge current to 100mA or so. Are there any other MAX1555 alternatives ...
2k views

### Need help driving N FET gate from LM393 comparator output

I am working on a charge controller circuit idea I had. The circuit 'works' meaning it achieved desired output voltage but the fet doesn't seem to be turning all the way on so lots of heat is ...
108 views

### Very low power: Most power-efficient way of storing charge for hours

I'm researching the feasibility of doing an art project that involves soaking up ambient RF power in a city (energy harvesting) and then playing a 1 second sound clip through a speaker as soon as ...
193 views

### Will a trickle charge lead-acid battery system last?

If I were to implement a simple battery backup system like this to power several WiFi radios in a field situation, how would the battery handle it? Would trickle charging it like that wear it out ...
957 views

### How and when can solar charge controllers be stacked together?

I run a small busniness selling solar charge controllers. Often I have a problem with not having controllers rated high enough amp-wise. I know that charge controllers can be stacked. But can all be ...
155 views

### Calculating induced charge

Let's say I have a battery with V volts. A conductive material (Material A) is connected only to the battery's positive terminal. Material A is then connected to a second conductive material (Material ...
66 views

### Solar charge controller low wattage panels

Do I need a solar charge controller for low watt/low battery voltage situations? This site says that they are generally not needed: http://www.solar-electric.com/solar-charge-controller-basics.html ...
64 views

### Do the recombination of charge carriers cause the diode to stop conducting?

This might be a stupid question but I am either having a mental block or I'm getting something. I'm learning about excess minority charge carriers. So, when an electric field is applied across a pn ...
2k views

### Voltage requirements for charging Nokia phone

I have an old Nokia phone which charges fine from the adaptor, but refuses to charge using a USB charging cable. Note that this isn't a normal USB cable, as you can see from the picture, it's got a ...
170 views

### What parameters affect battery charge time?

What parameters affect battery charge time? For example if we're interested in designing a charger for mobile batteries, what parameters should be considered? What happens if a little higher voltage ...
68 views

### Find current flowing over an element given charge as a function of time

This should be pretty basic but I want to clarify some: I = dQ/dt, so that means that I is the derivative of q(t) right? So if I'm given q(t) = (7t^2 - 2t +3) pC and told that time is dimensionless ...
132 views

### Charge moves if you scuff the rag with your shoes [closed]

Why is that when you scuff with your shoes on, charges move (since electrometer moves back and forth), but if you dont have your shoes on, the electrometer doesnt move Here is the corresponding video ...
110 views

### Charging Capacitors Multiple Times [closed]

I was thinking about "charging" capacitors. If you had a circuit like this: simulate this circuit – Schematic created using CircuitLab As you can see, the 10 milivolt power source will ...