eli5 dry battery cell has 1.5 volts. what’s the rationale of different sizes of cells having same 1.5 volts? are they meant for space accomodations or more power?
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Think of electricity like it’s water in a pipe. The pipe represents the wire that the electricity travels through. Electrical current is analogous to how much water is flowing through the pipe over a period of time. Electrical voltage is analogous to water pressure in the pipe. Like, if the pipe travels vertically for a while, the water at the bottom of that vertical run of pipe will be at higher pressure than the water at the top. That difference in pressure between the top and bottom is analogous to the voltage across a battery. It’s basically how forcefully the electricity is being pushed through the wire.
Now imagine that this whole system of water and pipes is being fed by a tank of water. The water slowly empties out of the tank, and flows through the pipes. When the tank is empty, no more water flows through the pipes. As you can probably imagine, the tank is analogous to the battery.
So, imagine you have two different water systems with pipes and tanks. They’re identical except one has a much larger tank of water than the other one. The water pressure in the pipes is the same, and so is the rate of water flowing through the pipes. However, the system with the larger tank will take a lot longer to empty out.
This is the same with different size batteries. You can have a AAA battery and a D battery, and they have 1.5 volts across their terminals. If you hook them both up to a circuit, they’ll both cause the same amount of electricity to flow through that circuit. However, the D battery will last a whole lot longer than the AAA battery. That’s the only difference.
Battery capacity is usually expressed in mAh (milli-amp hours). Milli-amps are a measure of electrical current. So, you multiply the number of milli-amps the battery is putting out times the number of hours that it can put out that current, and that’s mAh. If the battery can put out 200 mA for 1 hour, that’s 200 mAh. If it can put out 100 mA for 6 hours, that’s 600 mAh.
AAA batteries have a capacity of 1200 mAh. AA batteries are 2000-3000 mAh. D batteries are usually 8000+ mAh (some types are even closer to 20,000 mAh). They all have 1.5 volts across their terminals, meaning they all push electricity through the circuit with the same force, but some have bigger “electron tanks” than others.
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