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P18_circuits(1) - Batteries The Electric Battery A battery...

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Batteries
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The Electric Battery A battery transforms chemical energy into electrical energy . Chemical reactions within the cell create a potential difference between the terminals This potential difference can be maintained even if a current is kept flowing. + terminal - terminal
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Red-Ox reaction Copper (Cu) binds its electrons stronger than iron (Fe). We can release energy by moving electrons from iron to copper. Voltage = Energy / charge
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The interior of a battery (appendix AA-66)
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Battery capacity The capacity of a battery is measured in Ampere hours (A h) 1 A h = 1 A * 3600 sec = 3600 Coulomb i.e. this is a measurement of charge The stored energy is also depends on the battery voltage Energy = Voltage * charge
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Example A battery is labeled 10 A h, 10V. What energy can the battery store? A) 100 J B) 100 V*A C) 36 kJ D) 18 kJ
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Batteries in series 1.5 V 3 V 1.5 V Like two escalators one above the other. This doubles the height of the escalator.
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Batteries in parallel 1.5 V 1.5 V Like two escalators in parallel, they cover the same height, but increase the capacity.
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Using batteries You have several of the depicted NiMH AA batteries (1.25V). Your device requires 2.5V. Additionally a battery capacity of 5Ah is recommended to ensure the desired operational lifetime. Which battery configuration do you choose? A) B) C) D) E)
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Batteries and Capacitors Batteries can store much more energy than capacitors of the same size. But capacitors can release the energy much quicker . Batteries are limited by the speed of the chemical reaction. E.g camera flash uses capacitors, charged by batteries
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Example problem A 1 F capacitor is charged with a 9V battery. Then a switch is thrown and the capacitor is discharged through a resistor.
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