The size of a capacitor is measured in units called farads The degree of overlap between the plates alters the capacitance and that's what tunes the radio into a particular station. This rotates a set of thin metal plates so they overlap to a greater or lesser extent with another set of plates threaded in between them. When you turn the dial with your finger, you turn an axle running through the capacitor. Photo: This variable capacitor is attached to the main tuning dial in a transistor radio. Such as mica and glass, paper soaked in oil, In most electronic circuits, theĬapacitors are sealed components with dielectrics made of ceramics The tuning is carried out by a large variable capacitor that Capacitors useĭielectrics made from all sorts of materials. The third way is to make theĭielectric as good an insulator as possible. One is to increase the size of the plates. There are three ways to increase the capacitance of aĬapacitor. The bigger the capacitance, the more electricity a capacitor can The size of a bucket: the bigger the bucket, the more water it can store The capacitance of a capacitor is a bit like The amount of electrical energy a capacitor can store depends on Voltage in circuits, for tuning (in radios and TVs), and for a (circuits that allow only certain signals to flow), for smoothing the They can be used as timing devices (because it takes aĬertain, predictable amount of time to charge them), as filters The motor or lamp until there's none remaining on the plates.Īlthough capacitors effectively have only one job to do (storingĬharge), they can be put to all sorts of different uses in electricalĬircuits. Motor or a flash bulb, charge will flow from the capacitor through But if you connect theĬapacitor to a second circuit containing something like an electric (though it may slowly leak away over time). You disconnect the power, the capacitor keeps hold of its charge One plate gains a positive chargeĪnd the other plate gains an equal and opposite (negative) charge. When you turn on the power, an electric charge You can charge a capacitor simply by wiring it up into anĮlectric circuit. Artwork courtesy of US Patent and Trademark Office from US Patent 2,089,683: Electrical capacitor by Frank Clark, General Electric, August 10, 1937. The foil sheets are connected to terminals (blue) on the top so the capacitor can be wired into a circuit. Second, the dielectric is sometimes made of toxic or corrosive chemicals that can burn your skin.Īrtwork: How an electrolytic capacitor is made by rolling up sheets of aluminum foil (gray) and a dielectric material (in this case, paper or thin cheesecloth soaked in an acid or other organic chemical). WARNING: It can be dangerous to open up capacitors. The whole thing is wrapped up into a compact cylinder and coated in a protective metal case. The "plates" are two very thin sheets of metal the dielectric an oily plastic film in between them. Photo: Inside, an electrolytic capacitor is a bit like a Swiss roll. Thin metal legs you can hook into an electric circuit. The two plates inside a capacitorĬonnections on the outside called terminals, which are like Largely for historic reasons) and there's the insulator in between There are the two conductors (known as plates, Zap!Ĭapacitors come in all shapes and sizes, but they usually have the In an instant through the xenon flash bulb. Once the capacitor is fully charged, it can release all that energy Why you typically have to wait a little while.)
(It takes time to charge a capacitor and that's To the flash gun charges up for a few seconds using energy from yourĬamera's batteries. Huge burst of light in a fraction of a second. If you're takingĪ flash photograph, for example, you need your camera to produce a A capacitor generally releasesĮnergy much more rapidly-often in seconds or less. It very slowly through a circuit sometimes (in the case of a quartz A battery uses chemicals to store electrical energy and release Photo: A small capacitor in a transistor radio circuit.ĭo. To a capacitor is called charging releasing the energy from a Something that can store electrical energy. Through them) and separate them with an insulator (a materialĭoesn't let electricity flow very well) and you make a capacitor: Take two electrical conductors (things that let electricity flow