The pictured capacitors have a tolerance of ±1%.

From the left in the photograph
Capacitance: 0.01 µF (printed with 103F)
[the width 7mm, the height 7mm, the thickness 3mm]
Capacitance: 0.022 µF (printed with 223F)
[the width 7mm, the height 10mm, the thickness 4mm]
Capacitance: 0.1 µF (printed with 104F)
[the width 9mm, the height 11mm, the thickness 5mm]

Care must be taken when using a capacitor with such a large capacitance in power supply circuits, etc. The rectifier in the circuit can be destroyed by a huge rush of current when the capacitor is empty. For a brief moment, the capacitor is more like a short circuit. A protection circuit needs to be set up.

The size is small in spite of capacitance. Physically, the diameter is 21 mm, the height is 11 mm.

Care is necessary, because these devices do have polarity.

In this article, we'll learn exactly what a capacitor is, what it does and how it's used in electronics. We'll also look at the history of the capacitor and how several people helped shape its progress.

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.

The capacitor is constructed with two electrode plates facing eachother, but separated by an insulator.

When DC voltage is applied to the capacitor, an electric charge is stored on each electrode. While the capacitor is charging up, current flows. The current will stop flowing when the capacitor has fully charged.

When a circuit tester, such as an analog meter set to measure resistance, is connected to a 10 microfarad (µF) electrolytic capacitor, a current will flow, but only for a moment. You can confirm that the meter's needle moves off of zero, but returns to zero right away.

When you connect the meter's probes to the capacitor in reverse, you will note that current once again flows for a moment. Once again, when the capacitor has fully charged, the current stops flowing. So the capacitor can be used as a filter that blocks DC current. (A "DC cut" filter.)

However, in the case of alternating current, the current will be allowed to pass. Alternating current is similar to repeatedly switching the test meter's probes back and forth on the capacitor. Current flows every time the probes are switched.

Three prefixes (multipliers) are used, µ (micro), n (nano) and p (pico):

• µ means 10-6 (millionth), so 1000000µF = 1F
• n means 10-9 (thousand-millionth), so 1000nF = 1µF
• p means 10-12 (million-millionth), so 1000pF = 1nF

Capacitor values can be very difficult to find because there are many types of capacitor with different labelling systems!

There are many types of capacitor but they can be split into two groups, polarised and unpolarised. Each group has its own circuit symbol.

The standard unit of capacitance is the farad, abbreviatedF. Thisis a large unit; more common units are the microfarad, abbreviated µF (1 µF =10-6F) and the picofarad, abbreviated pF (1 pF = 10-12 F).

Capacitors can be fabricated onto integrated circuit (IC)chips. They are commonly used in conjunction with transistors in dynamic random access memory (DRAM). The capacitors helpmaintain thecontents of memory. Because of their tiny physical size, thesecomponents have lowcapacitance. They must be recharged thousands of times per second or theDRAM willlose its data.

Large capacitors are used in the power supplies of electronicequipment ofall types, including computers and their peripherals. In these systems,thecapacitors smooth out the rectified utility AC, providing pure, battery-likeDC.

Right now, desalinting seawater largely revolves around pressurizing water and forcing it through a membrane to purify it. The process takes a lot of energy and hence a lot of cost. Desalinating seawater can cost as much as 50 cents a liter.

A collection of private companies and research institutes in Spain have begun to experiment with capacitive deionization for purifying seawater. In this, two electrodes would be placed in a tank. The ions (i.e., salt particles) would be drawn to one electrode. The ions would absorb the ions, which could then be released in a regeneration cycle. Capacitive purification was considered in the past, but the materials were too expensive. So who knows, it might work now.

The price of aluminum electrolytic capacitors has been stable since August 2008, while the price of aluminum foil continues to drop, lowering Lelon's cost pressure. However, order visibility for aluminum electrolytic capacitors is still low, the company noted.

Lelon has entered the wind power market with its large-size capacitors, and plans to apply the product to other applications. The company has already shipped a small volume of large-size capacitors to a motorcycle maker and expects to expand into the automotive segment.