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In extreme cases, battery chemicals may spray violently from the casing and cause injury. If leakage occurs, either spontaneously or through accident, the chemicals released may be dangerous. Liquefaction necrosis may occur because sodium hydroxide is generated by the current produced by the battery (usually at the anode). Rechargeable battery Tips. NIMH Technology Information. NiMH cells, although similar in chemistry, suffer less from memory effect. Low-capacity NiMH batteries (1,700-2,000 mA·h) can be charged some 1,000 times, whereas high-capacity NiMH batteries (above 2,500 mA·h) last about 500 cycles. For example, disposable batteries often use a zinc "can" both as a reactant and as the container to hold the other reagents. In the above example, the number in the second bracket can be used for conversion between values of specific resistance in the metric system and in the imperial system. Table 3 also indicates the electric resistance per 1000 m and 1000 ft of these wires.

More recently, carbon fiber reinforcement cables have been introduced; instead of steel, these electric cables have strands of carbon fiber composite material in the middle. Older children do not have problems with batteries smaller than 21-23 mm. Ingested disk batteries do not usually cause problems unless they become lodged in the gastrointestinal tract. It may also cause damage to the charger or device in which the overcharged battery is later used. Deep Cycle Battery FAQ Archived 22 July 2010 at the Wayback Machine. Deep cycle battery guide Archived 17 February 2009 at the Wayback Machine. In the United States, the Mercury-Containing and Rechargeable Battery Management Act of 1996 banned the sale of mercury-containing batteries, enacted uniform labeling requirements for rechargeable batteries and required that rechargeable batteries be easily removable. The active chemical leakage can then damage or disable the equipment that the batteries power. It is easy to understand, therefore, that whereas the resistance of a wire can be almost constant, its ampacity depends on the temperature and some other working conditions, and it cannot be a constant. Specific resistance: Same as resistivity: the electric resistance of a specific size (based on the measurement system) of a metal or material.

The resistance of a piece of any material (even an insulator) to the flow of electricity is proportional to its length and inversely proportional to its cross-section area. In the metric system, ρ is the resistance of a piece of metal (10 mm × 10 mm × 10 mm), that is 1 cm long and has a cross-section of 1 cm2 (see figure below). Some typical ones are shown in Figure 6. For the final distribution to consumers" poles of approximately 12 m (40 ft) are used, and the height of larger structures varies between 18 and 42 m (60 and 140 ft). Its unit in the metric system is, thus, 1/ohm-meter. Also shown in the table is the temperature coefficient, which represents how much the specific resistance of a metal changes with temperature. It is very important to know the resistance of electric conductors when they are used in electric circuits. Figure 8 A three-conductor underground electric cable.

Figure 1 For various reasons including transportation, conductors must be flexible. See Figure 1. To increase the flexibility of thicker conductors, they are made of several strands. Ampacity is determined based on the amount of heat generated in a conductor owing to the current and the fact that this heat must be taken away so that the conductor temperature does not increase anymore beyond a certain safe level. Ampacity is determined based on the heat generated in a conductor due to the current through it. In addition to this property, for wires and cables, there is another property that determines how much current is allowed to pass through a conductor. You realize that when a light bulb is on, the temperature of the filament is much more than room temperature, and, therefore, the resistance of its filament is several times larger than when at room temperature. R depends also on the material; for example, copper is a much better conductor than iron.

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