0
Theoretically, forever, because as the voltage on the capacitor approaches the source voltage, the available current to charge the capacitor approaches zero.
In practice, however, it simply depends on what you call "charged".
In the simple example of a capacitor being charged from a voltage source in series with a resistance, the voltage is given by ...
VT = Vs (1 - e -T/RC)
... so, if your definition of "charged" is 99% of VT then T would have to be 5 RC's or 5 time constants.
If a resistor is connected in series with the capacitor forming an RC circuit, the capacitor will charge up gradually through the resistor until the voltage across the capacitor reaches that of the supply voltage. The time called the transient response, required for this to occur is equivalent to about
5 time constantsor
5T
. This transient response time
T
, is measured in terms of
τ= R x C
, in seconds, where
R
is the value of the resistor in ohms and
C
is the value of the capacitor in Farads. This then forms the basis of an RC charging circuit were
5T
can also be thought of as
"5 x RC"
.
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Do capacitors store electrical energy?
Capacitors act like tiny storage batteries made of two plates separated by a thin insulator or air. When one plate is charged negative and the other positive, they build up a charge that remains when the current is removed. When its power is required, the circuit is switched to conduct current between the two plates, and the capacitor releases its charge.AnswerCapacitors don't really store charge at all. They allow negative charge to be transferred from one plate to the other, thus establishing an electric field between their plates. But there is no net increase in charge -the amount of charge on the capacitor's plates, after 'charging', is exactly the same as there was before 'charging' -it's just moved around! What capacitors 'store' is energy, not charge.
How does a capacitor work?
In a way, a capacitor is a little like a battery. Although they work in completely different ways, capacitors and batteries both store electrical energy. Inside the battery, chemical reactions produce electrons on one terminal and absorb electrons on the other terminal. A capacitor is much simpler than a battery, as it can't produce new electrons -- it only stores them. Inside the capacitor, the terminals connect to two metal plates separated by a non-conducting substance, or dielectric. You can easily make a capacitor from two pieces of aluminum foil and a piece of paper. It won't be a particularly good capacitor in terms of its storage capacity, but it will work. In theory, the dielectric can be any non-conductive substance. However, for practical applications, specific materials are used that best suit the capacitor's function. Mica, ceramic, cellulose, porcelain, Mylar, Teflon and even air are some of the non-conductive materials used. The dielectric dictates what kind of capacitor it is and for what it is best suited. Depending on the size and type of dielectric, some capacitors are better for high frequency uses, while some are better for high voltage applications. Capacitors can be manufactured to serve any purpose, from the smallest plastic capacitor in your calculator, to an ultra capacitor that can power a commuter bus. NASA uses glass capacitors to help wake up the space shuttle's circuitry and help deploy space probes. Here are some of the various types of capacitors and how they are used. Air - Often used in radio tuning circuits Mylar - Most commonly used for timer circuits like clocks, alarms and counters Glass - Good for high voltage applications Ceramic - Used for high frequency purposes like antennas, X-ray and MRI machines Super capacitor - Powers electric and hybrid cars Capacitor Circuit In an electronic circuit, a capacitor is shown like this: When you connect a capacitor to a battery, here's what happens: • The plate on the capacitor that attaches to the negative terminal of the battery accepts electrons that the battery is producing. • The plate on the capacitor that attaches to the positive terminal of the battery loses electrons to the battery. Once it's charged, the capacitor has the same voltage as the battery (1.5 volts on the battery means 1.5 volts on the capacitor). For a small capacitor, the capacity is small. But large capacitors can hold quite a bit of charge. You can find capacitors as big as soda cans that hold enough charge to light a flashlight bulb for a minute or more. Even nature shows the capacitor at work in the form of lightning. One plate is the cloud, the other plate is the ground and the lightning is the charge releasing between these two "plates." Obviously, in a capacitor that large, you can hold a huge amount of charge! Let's say you hook up a capacitor like this:Here you have a battery, a light bulb and a capacitor. If the capacitor is pretty big, what you will notice is that, when you connect the battery, the light bulb will light up as current flows from the battery to the capacitor to charge it up. The bulb will get progressively dimmer and finally go out once the capacitor reaches its capacity. If you then remove the battery and replace it with a wire, current will flow from one plate of the capacitor to the other. The bulb will light initially and then dim as the capacitor discharges, until it is completely out. Farad A capacitor's storage potential, or capacitance, is measured in units called farads. A 1-farad capacitor can store one coulomb (coo-lomb) of charge at 1 volt. A coulomb is 6.25e18 (6.25 * 10^18, or 6.25 billion billion) electrons. One amprepresents a rate of electron flow of 1 coulomb of electrons per second, so a 1-farad capacitor can hold 1 amp-second of electrons at 1 volt. A 1-farad capacitor would typically be pretty big. It might be as big as a can of tuna or a 1-liter soda bottle, depending on the voltage it can handle. For this reason, capacitors are typically measured in microfarads (millionths of a farad). To get some perspective on how big a farad is, think about this: • A standard alkaline AA battery holds about 2.8 amp-hours. • That means that a AA battery can produce 2.8 amps for an hour at 1.5 volts (about 4.2 watt-hours -- a AA battery can light a 4-watt bulb for a little more than an hour). • Let's call it 1 volt to make the math easier. To store one AA battery's energy in a capacitor, you would need 3,600 * 2.8 = 10,080 farads to hold it, because an amp-hour is 3,600 amp-seconds. If it takes something the size of a can of tuna to hold a farad, then 10,080 farads is going to take up a LOT more space than a single AA battery! Obviously, it's impractical to use capacitors to store any significant amount of power unless you do it at a high voltage. Applications The difference between a capacitor and a battery is that a capacitor can dump its entire charge in a tiny fraction of a second, where a battery would take minutes to completely discharge. That's why the electronic flash on a camera uses a capacitor -- the battery charges up the flash's capacitor over several seconds, and then the capacitor dumps the full charge into the flash tube almost instantly. This can make a large, charged capacitor extremely dangerous -- flash units and TVs have warnings about opening them up for this reason. They contain big capacitors that can, potentially, kill you with the charge they contain. Capacitors are used in several different ways in electronic circuits: • Sometimes, capacitors are used to store charge for high-speed use. That's what a flash does. Big lasersuse this technique as well to get very bright, instantaneous flashes. • Capacitors can also eliminate ripples. If a line carrying DC voltage has ripples or spikes in it, a big capacitor can even out the voltage by absorbing the peaks and filling in the valleys. • A capacitor can block DC voltage. If you hook a small capacitor to a battery, then no current will flow between the poles of the battery once the capacitor charges. However, any alternating current (AC) signal flows through a capacitor unimpeded. That's because the capacitor will charge and discharge as the alternating current fluctuates, making it appear that the alternating current is flowing.
Would a 450V parallel plate capacitor made from copper or aluminum foil melt when discharged through a circuit of about 1 ohm?
There's no reason for the capacitor to heat up, because it's only storing energy,not dissipating it. When you discharge the capacitor, the energy flows out andthrough the external circuit, and that's where it dissipates. If anything is going tomelt or explode, it's going to be something outside of the capacitor, through whichyou try to jam the energy.Which brings us to the 1-ohm resistor . . .You have said that you have a "450V" capacitor. The rating marked on a capacitorisn't the voltage across it when it's charged ... that can be whatever you make it.The marking is the maximum that the capacitor can hold without arcing acrossbetween the plates ... the number is called the "maximum working voltage".You can try to charge a capacitor to whatever voltage you want, but it won'thold any more than the number marked on it.In order to discuss the fate of that 1-ohm resistor, we have to know what theinitial charge is on the capacitor. The only number given in the question is 450V,and even though that's more likely the "max working voltage" of the capacitor,let's assume for the moment that the capacitor is actually charged up to 450 volts DC.The charging is complete, the staff retreats behind their bullet-proof plexiglassbunker, puts on their dark glasses, and prepares to push the button that willremotely close the circuit and discharge the capacitor through the 1-ohmresistor. The button is pushed, and here's what the high-speed camera revealsafter the smoke clears and the fire units have departed:As the energy drains from the capacitor, the voltage on it steadily dwindles.How fast it dwindles depends on the resistance of the external circuit, and onthe "capacitance" of the capacitor (which tells us how much energy it takes tocharge it up to any given voltage).What we do know about this circuit is that the capacitor is charged initially to450 volts, and that it discharges through 1 ohm. This is enough for us tocalculate the initial current at the instant the switch is closed ...I = (450 volts)/(1 ohm) = 450 Amps.We can also calculate the power dissipated by the resistor at that instant:P = I2 R = (450)2 x 1 = 202.5 kilowatts ... roughly the power that would bedemanded of a car battery if it had to start 85 cars all at the same time!Regardless of the capacitance, and how quickly the charge on the capacitordwindles down from 450 volts, it's likely that this initial surge through the1-ohm resistor causes it to self-destruct like a pellet of plutonium on thetower at White Sands.To answer the question:Your capacitor is safe from harm. But if you're going to discharge it through 1 ohm,then please wear gloves, safety glasses, and a kevlar apron.
Does a magnetic fIEld have an effect on a capacitor placed in between the plates?
Does a magnetic field have an effect on a capacitor when it is placed between the plates? Yes, a magnetic field between the plates of a capacitor would have some effect. Without more information it is difficult to determine how much.
How much electricity was required to energize the flux capacitor IN Back to the Future?
1.21 Gigawatts
Why is there a C in the equation for a discharging capacitor?
The C represents the capacitance (in farads) of the capacitor. It is a measure of how much charge a capacitor can hold. This is needed to know how much energy the capacitor is holding.
What happens to the charge if you double the voltage across a capacitor?
In order to double the voltage across a capacitor, you need to stuff twice as much charge into it.
What electronic components can store charge?
A capacitor and a battery. They both store charges but due to the fact that conventional batteries are chemically-powered, they don't charge or discharge very fast. On the other hand, they can be built to hold large amounts of charge. Conversely, a capacitor doesn't have nearly the same amount of capacity as batteries, but they charge and discharge much faster. For this reason, they are used in many capacities, such as in vehicle ignition systems, charging circuits for conventional digital cameras, and some appliances (and hence why those appliances will urge you to not open them up yourself as you may be exposed to enough charge that will kill you).
If a 0.40-uF capacitor is connected to a 9.0-V battery how much charge is on each plate of the capacitor?
The units of capacitance are called farads. A one farad capacitor is a capacitor with 1 volt potential difference with 1 coulomb of charge on the capacitor, C = Q/V or Q=CV So the charge held on your capacitor is Q = CV = 9Volts * 0.40*10-6Farads=3.6*10-6 Coulombs
How much charge is in a 6800-μF capacitor with 50 V across it?
50V
A farad is a measure of what?
The Farad is a measure of how much electric charge is accumulated on the capacitor. Named after Michael Faraday
What is an importance of capacitance?
capacitor is a device to store charge .it is based on the concept that when the potential of the capacitor is decreased it can gain some more charge so Q = CV where V is potential and Q is the charge stored then C is the capacitance. capacitance is the ability of the capacitor to store charge. expression for capacitance is C=ɛA/d where ɛis permittivity and A is area of capacitor plates ,d is plate separation.
How can you store a different amount of charge in a capacitor?
Power = V*I Power = (V) * (C*dV/dt) To store more / less power / charge, charge the capacitor with a greater / smaller voltage (make sure the cap is rated for at least as much as the voltage you are charging from, though).
How much charge flows from each terminal of a 16.0 V battery when it is connected to a 8.80 F capacitor?
if the capacitor is not initially charged then it will receive during its charging an electric charge Q given by Q=V/C=16/8.8 = 1.82 microcoulomb
How much time it will take to charge a 20 farad 3v capacitor with 0.5v 8w solar module?
The capacitor requires (1/2 * 20F * 3V * 3V) = 90 joules of energy to charge. Assuming perfect conversion, a steady 8W of power will provide that much energy in 11.25 seconds.A 20F capacitor is gigantic, though, so I'm assuming this isn't a real-world scenario!
What are the advantages and disadvantege of capacitors?
Capacitors are very good for storing small quantities of electrical energy, for creating timing circuits based on the time it takes a capacitor to charge, and there are also excellent uses of their characteristic of conducting a varying voltage.
What does a capacitor store if the sum of charges of both capacitors is zero?
it may consist much of negative and positive chargeAnswerA capacitor stores energy within an electric field set up between its plates. It does not 'store' charage, as the net charge is the same both before and after the capacitor has been 'charged' (unfortunate use of the word!). What it does is to enable charge to be separated, with one plate then becoming negative with respect to the other, resulting in an electric field between the two plates.When we describe the 'amount of charge' on a capacitor, by convention, we mean the amount of negative charge stored on its negative plate, and not the sum of this and the amount of positive charge on its positive plate!
