Questions tagged [charge]

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

Electric charge is a fundamental physical property of different particles. Each particle has a charge which is either positive, negative, or neutral (also called having no charge). Electrons have negative charge.

Charged particles exert a force on each other. Like charges repel, opposite charges attract.

The motion of charge is electric current. By convention, we refer to current as flowing in the direction positive charges are flowing. Since electrons have negative charge, electron flow is opposite from current flow. This has minimal significance for most purposes.

In some cases, an imaginary particle called a "hole" is posited. A hole has positive charge. In physical reality, a hole is the absence of an electron. It is sometimes useful to model this absence as a particle.

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What is a Charge?

I'm a high school student. I love computers and electronics. Few weeks ago, I thought to build my own electronic gadget but, unfortunately I had not much knowledge in electronics. So, I decided to learn. After Googling here and there, I came across…
seek_learn_joy
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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 touchscreens, as I'm sure everyone here knows are…
Jeff Ryan
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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 electrons return to their source? Do the electrons…
Ranjit
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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?
JingleBells
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Does changing the gap between plates change the capacitor voltage?

Consider an ideal capacitor which has a length of \$\ell_1\$ between its plates. The capacitor terminals are open; they are not connected to any finite valued impedance. Its capacity is \$C_1\$ and it has an initial voltage of \$V_1\$. What happens…
hkBattousai
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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 battery over time which may or may not have protection…
s3c
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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 and is therefore negative; while cation has cat…
HellaMad
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Why does a sweaty finger neutralise the touch-sensor on my phone screen?

My experience is that when I'm running, my fingers "don't work" on my phone screen. My understanding was that the sensor on a touch screen works on static-charge, ie that you act as an 'earth' to the screen and it can sense the difference in…
hawkeye
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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 at extremely low currents. Combing your hair on a…
Firdous
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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 around 10% larger (I suppose primarily in…
Alex I
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Why is the energy in a battery QV, but the energy in a capacitor QV/2

If I know the total charge in a battery, let's say 5000 Ah, and I want to find how much energy is stored in the battery, I multiply the total charge by the voltage E = Q·V; for example, for 12 V I will get 12·5000. Now if I know the charge in a…
bibo999999
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Would an electric fence be able to detect being bypassed?

In the Flashpoint episode "The Farm," there's a scene where you can see one of the officers run a jumper cable from one contact on an electric fence to another, then cut the line of the fence (not breaking the circuit, mind you). Based on context…
Der Kommissar
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How can a capacitor store charge whilst also passing current?

It's frequently said that capacitors store charge. Just reading through Wikipedia, I find: Daniel Gralath was the first to combine several jars in parallel into a "battery" to increase the charge storage capacity. Benjamin Franklin investigated the…
Phil Frost
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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 discharge with certain voltage and current values over…
Cookiebuster
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Self capacitance of an isolated object

A few times I've been reminded that an object can have self capacitance and it's just not registering with me how this can be so. I'm sure there's a good explanation. Here's the explanation I am usually given but I'm still not grasping that…
Andy aka
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