Alapveto egyenletek utazashoz, kalandturahoz

Kezdőlap utazas.com Fórum Nagyvilág Alapveto egyenletek utazashoz, kalandturahoz

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  • #4504 Hozzászólás

    Oveges

    Fizikusok, kemikusok, matekosok.

    Melyek azok az alapveto egyenletek, atszamitasok, stb. ami jol jon egy komolyabb, expedicio jellegu, utazasnal. Pl. elemek kapacitasanak kiszamitasa ut elott egy adott szerkentyuhoz, vagy barmi mas…?

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  • #95356 Hozzászólás

    fari

    ez nem egy magyar fórum, ember!

    #95355 Hozzászólás

    Tanar Ur

    Elemi problemak

    For electric current you will see abbreviations like A, mA, Amp, Ampere, milliAmp, milliAmpere, etc. For example, a 100 watt light bulb will have about 1 Amp flowing through it (1000 mA…right?). A digital camera will have an average current of around 50 mA to 350 mA…depends upon whether or not you have your LCD screen on, and amount of clicking and flashing is going on.

    mA, however, is not really how much charge…it is the rate of depletion (or charging rate) for a battery. For example, a battery capacity of 1800 mAH can deliver 100 mA for 18 hours…or 200 mA for 9 hours, or 300 mA for 6 hours, and so on.

    Let’s say your digital camera uses an average of 307 mA and has a battery with a capacity of 1800 mAH (really high battery capacity!!). If you divide 1800 by 307, that will leave you with about 5.9 hours before you have to replace or recharge the battery.

    1800 mAH / 307 mA = 5.902 hours, or 5 hours and 54 minutes, that’s a right good amount of time!!

    Finally, batteries are small and cannot sustain real high currents for any length of time. For example, a battery having a battery capacity of 1800 mAH cannot deliver 7200 mA (7.2 amps) continuously for one quarter hour, it will turn into a cigarette lighter within a few minutes!!

    But it can deliver large amounts for less than a second. Like cash flow, you get short periods of high usage, longer periods of medium usage, and very long periods of little usage…it’s the average usage over time that is considered for battery capacity and cash flow.

    Why is battery capacity important?

    Battery capacity is important to you because it will determine how long your digital camera will operate before you have to replace or recharge the battery set.

    If you are shooting pics, one right after another, with the LCD on, inside using flash, how long will your camera batteries last?

    If your battery capacity is only good for one hour in continuous shooting, and you need to shoot for three hours you have some options:

    1. You can stop shooting, not a good alternative at a wedding…

    2. You can keep your camera hooked up to the wall socket power source, but that is a little cumbersome sometimes…hard to move around much…

    3. You can swap out the batteries two or three times, this is better…

    4. You can swap out the batteries, and put the spent batteries into a battery charger, maybe three or four battery sets being simultaneously recharged, best of all.

    If you get a battery charger, you want it to recharge a battery within that hour, 30 minutes is safe enough…gives you more time to choose when to swap out the camera batteries.

    Say your battery can charge up to 1800 mAH…and it is down to 80 mAH of charge, but still delivering that required current for a short while longer…you gotta pump back 1000 mAH of charge…what if you had a good strong charger that can pump in at a 3000 mA rate? (3.0 Amps…wow!! Can’t do that for a tiny fella…again, it is a battery not a cigarette lighter!! But, hypothetically speaking…) Yep, it will pump in that 1000 mAH of charge in about 1 / 3 hour or 20 minutes…you can have enough batteries charging so you can rotate ’em through and give ’em time to pump up.

    Notice that batteries get hot when larger currents pass through them…doesn’t matter if they are delivering that current or being recharged…it’s still current through a relatively small device.

    The single NiMH battery cell produces about 1.3 volts. To pump charge in at a current of 1.0 A (1000 Ma), that will be 1.3 watts (volts x amps); watts is where temperature comes from. For an AAA battery, 1.3 watts won’t cook that little fella, it’ll get warm…but, 10 amps and 13 watts leads to sizzle, smoke, snap, crackle, pop. There’s just not enough room to dissipate that much energy fast enough.

    Back to our 100 watt light bulb with 110 volts and about 1 amp, why does it get white hot? Because its the 110 volts “shoving” that charge though a more “resistive” element. Pushing with a 1.3 volt potential to get one amp through an NiMH battery is not so hard to do, not much resistance, not much “friction”, nothing gets white hot.

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