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Show CONDENSER ACTS AS STORAGE TANK How the Fixed and Variable Types Are Constructed and What They Do. A eondenser in a radio circuit is a storage tank for electrical charges. This storage unit may be either fixed or variable. The fixed condenser, which consists principally of a few sheets of metal foil, intersectioned between be-tween parufmed paper or mica and bound tightly together, and which, unlike un-like the variable coudenser, does not cost very much either to buy or build, Is the one generally used on the receiving re-ceiving circuit of the vacuum tube. When Connected across the terminals termi-nals of the receiver, the fixed condenser conden-ser has the property of discharging with great violence across these terminals ter-minals and setting up stronger currents cur-rents to act upon the magnet colls of the receiver. If the coudenser were left out of the circuit the receivers would still respond to the impulses of the detector's rectified currents, but when they are added to the circuit, these currents build Op a voltage in the condenser so great that when it is discharged it does so with violence. This discharge occurs at each impulse In the voice of the speaker. The voice Impulses set up in the condenser are forced to discharge immediately, in order to leave room for the next charge and to prevent the condenser's becoming overloaded. Just imagine a reservoir of water filling slowly until the water were up to brim, and then flood gates opened so that the water all ran out. This Is a good example of the manner in which the condenser ? 3 rJD'eecf-rc c I , I , 1 , 3 artery is charged and discharged. However, the radio Impulses come so fast that the condenser charges and discharges almost instantly. The low capacity fixed condenser In the grid circuit of the vacuum tube detector functions as a checking condenser con-denser for the radio currents to the plate of the tube and is generally about 0.0005 microfarads. Without this condenser In the tube circuit the signals will be much weaker and the bulb may have a tendency to choke up so that no plate circuit will flow through the circuit. Fixed condensers must be made of the best grade of materials ma-terials possible; that is they must possess high Insulating qualities so that the charges will not leak off through poor insulation. Condensers made of pure mica and copper foil are to be preferred over paper and tinfoil condensers, as (hey will build up their voltages to the highest point without leaking, before they suddenly discharge. dis-charge. Variable "widensers should also possess pos-sess Insulating qualities and such parts as insulating bushing and top plates should be made of good grade bakelite or equally good insulating material Filter washers and bushings soon develop de-velop leaks, as fiber has the property of absorbing moisture anil warps in time, cursing the plates in the condenser conden-ser to touch. Variable condensers are generally made from aluminum so as to make them as light as possible. I Aluminum has the property of keen-, keen-, Ing its shape in flat plates and Is also a good conductor. Built-up variable condensers with metal washers used as separators generally gen-erally give more satisfaction than other oth-er types. Experience has proved that they keep 1 heir plates separated without with-out scraping and the nunibei of plates can be increased or decrensec at will. A variable condenser lnsertci In series se-ries with the antenna and tuner decreases de-creases the wave length of tile antenna anten-na circuit as it is varied. When the plates are separated the wave length Is the shortcut, and even when the ! plates are internieslieil the wave I length Is shorter than If the condenser wore out of the circuit. A variable I condense! In shunt witli the secondary j or the i-.uiir.g coil will increase the wave lengtu uf the circuit, depending upon the numbr of plates that ara inserted in the condenser as it is varied va-ried from ISO degrees to lero. By reason of this characteristic the variable condenser allows for very close tuning. A condenser consists of two electrical electri-cal conductors separated by an Insulator. Insu-lator. The electrical conductors are called the plates aud the insulating medium separating the plates is called the dielectric. In Fig. I Is shown a simple condenser conden-ser consisting of two plates, A and B, with air between two plates acting as the dielectric. If now a battery C is connected to the two condenser plates, the positive side of the battery to one plate and the negative side to the other oth-er plate, a current will flow. Th's current cur-rent that flows from the battery terminals termi-nals when the battery is connected to the plates of the condenser Is called the charging current. During the process proc-ess of charging a condenser an elec-. trie displacement takes place In the dielectric. This electric displacement gives rise to an electromotive force which tends to. oppose the applied electromotive force from the battery C. Finally a point is reached where the hack e. m. f. and the charging cur rent become zero. If the battery C be disconnected from the condenser a potential difference differ-ence will exist between the two condenser con-denser plates that will just be equal to the potential of the battery C. Short-circuiting the condenser plates will cause the condenser to discharge, a condition that will exist until the potential difference between the plates has been reduced to zero or until the dielectric has again resumed its normal nor-mal state. The charge that can be placed on a static condenser depends upon three factors. First, the area of the condenser conden-ser plate3; second, the thickness and composition of the dielectric, and third, the potential difference applied to the plates by the battery. C. , |