Q&A for How to Build a Capacitor

Salt water is more conductive than plain water, so it will hold a charge better.

Some do. Electrolytic capacitors have the polarity marked. Hooked up backward, they pop and let the magic smoke out. Other types are not polarity sensitive.

Not necessarily. The capacitive effect occurs from the separation of the two plates (conductors). Not wrapping the bottom reduces the size of the plates (conductors), resulting in less capacitance, or a less capacitive effect, so you just have a smaller capacitor vs. the overall physical size of the unit that could have been utilized to maximize its energy potential.

Yes, the rate of both charge and discharge can be controlled by using an RC ("resistance/capacitance") circuit. For further information, look into "RC circuits" and "RC time constant" to find circuit designs that correspond with your needs.

You can use a multimeter to measure the voltage in your capacitor.

Just use a voltmeter to detect any potential difference or an ammeter to detect the presence of charges on the capacitor. You may also simply use an LED to see if it glows or not if you're not concerned with the numbers but simply want to know if it's charged or not.

Theoretically, a magnetic flux will be generated only during the charging or discharging of the capacitor in relation to the flow of current. Naturally, the higher the flow of electricity (amperage), the greater the amount of magnetic flux generated in relation to the movement of electrons. The direction of flow of the electricity will also have a direct effect on the physical shape of the magnetic flux as well. The shape of the magnetic flux, as well as the magnetic polarity, will change directions to the opposite side depending on the direction of electric flow.

If it can be charged with a household battery, which is a DC power source, then yes, it can be charged with a solar panel.

Not for long.

Ideally, as great as possible. Add salt and stir to dissolve it. If no solid salt remains, add more salt and stir. Repeat until the salt no longer dissolves, and stop—at this point, the water is saturated with dissolved salt, and using any more would be of no benefit.

Capacitance=Charge/Voltage; Charge=Current*Time. Therefore, use an ammeter to know how much current is flowing in one second. Take charge flow in one second and divide it with the volts of the battery which was used to charge the capacitor, and this is the capacitance of the capacitor.

Electrons always flow from low to high potential, so when the battery is connected to a capacitor electrons flow from the negative to the positive terminal of the battery reaching one plate where they get collected making the plate negatively charged. Electric field of the negative charges on this plate radiates inwards from the side of the next plate applying a force on the electrons of the next plate opposite to the electric field which causes them to move to the negative terminal of the battery thus completing the circuit.

Use 5v (add a resistor to the long leg of an l.e.d.), then attach from one side of capacitor the resistor leg of the l.e.d. (the positive lead). Attach the other l.e.d. leg (the negative lead) to the other side of capacitor. You charge by attaching the positive end of a 5v source to the base of the capacitor lead attached to the resistor. Attach the negative battery lead to the other side of the capacitor, let it charge momentarily, and then disconnect the battery. It should light up for a second.

Usually, if you have a red wire and a black wire, the red is positive and the black is negative. If you have a set of wires that have one being a solid color and the other the same but with stripes, the striped one is positive and the other is negative.

The charge is stored on the plates of the capacitor. When discharging the capacitor, the charges leave the plates. You can say the capacitor acts as a tiny battery.

No. A magnetic field will not charge a capacitor because the magnetic flux is just a byproduct of charging.

Yes it does, but it will light up the led only for a second or two. It can go up to three or four seconds if you use a resistor in the circuit. For a much more longer duration you must use several capacitors connected in parallel along with a resistor.

Of course. Any will suffice, but it will change the properties of the capacitor, depending on conductivity. Mainly it is the concentration of ions that will be affecting your performance.

In this case, the foil is the negative, as the charge is being held in the salt water. (Fun fact: you can draw energy from the salt water itself, without an external charge. Look up "Parallel Series Battery").

The battery can be of any size, depending upon the capacitance and voltage rating of the capacitor you are building.

Yes, you can. An electromagnetic pulse generator requires a capacitor to function.

What you are after is a magnetic connection from one plate over to the other plate, not a direct electron flow connection from one plate to the other. The magnetic flow connection will be strong enough to disturb or agitate into activity in the next plate by passing unhindered right through the center dielectric plate, and will not even see the dieletric plate. The quality, thickness or material the dielectric is made of will determine whether you can use high voltage, or low voltage. For example: High voltage you could use glass plates to separate conductor plate. Low voltage you could use plastic or acrylic sheets between conductor plates. You would design according to need and purpose.

The positive is the one where you plugged the positive pole of the battery when charging it.

Capacitors charge nearly instantly. You can plug a voltmeter to it: when it reaches the input voltage, then it's fully charged.

The current generated will depend on the load present on the circuit when you discharge the capacitor. If you're worried about how much the current is being output from the capacitor, put a resistor in series with the item you wish to protect. If you're thinking about how much energy you could feasibly get from this capacitor, just check the voltage, then check both terminals with an ammeter, and make a note of the value it outputs. Multiply the voltage by the current and that will give you the power in watts. Yes, you can touch the jar. The main thing you want to do is, to preserve the charge, is to not allow contact between the saline and the the tin foil. this would complete the circuit.