what are the purpose of voltage and current in a phone charger? How does it affect charging?
In: Technology
I find the electricity-water analogy useful for these things. Think of voltage as the pressure of the water, and current as the flow rate. In this case, the battery is a tank high up. You let out water from the tank into machinery to make the phone work. To charge the battery, you need to pump water up to it. This requires a certain pressure (voltage). To charge it quickly, you want to send water quickly. This is the current. So the more current, the faster the battery charges. Where this analogy breaks down is the limitations of fast charging. In a battery, if you try to feed it too much current, it will overheat. So the current needs to be carefully managed to flow as much as possible without overheating the battery.
So your question is a little vague. Do you want to know how voltage and current are related and why they are?
Well I’ll try to answer the questions asked an hopefully it makes sense.
Voltage is commonly thought as the pressure or the system, and current being the number of electrons. Well if you multiply the two together you get power.
P=V*I
Where:
P=power
V=Voltage
I=current
Well for phones, the battery is generally rated for 5ish volts. I say “ish” because your battery is probably 4.2 volts, but if you apply 4.2 volts then there is a zero difference and you get no current. So really our power equation could be written
P=V(SOURCE) – V(BATTERY) * I
So if battery and source is the same, the equation equals zero and you can’t charge anything. So instead we apply 5 volts and get a 0.8v difference. Them it’s a matter of how much current flow you have. That’ll be determined by the construction of the battery itself. In this case, every battery has a certain resistance to current and that’ll determine the current flow.
At the end of the day, batteries can only have so much current at a time. Think of it like friction, if you put too mush stuff moving too fast you get a lot of heat. And heat is really the thunkg that prevents us from charging too quickly
Voltage is the amount of force that the charger pushes each electron with, and current is the maximum number of electrons it can push (per second). Note that pushing without moving anything doesn’t actually use energy (think of leaning on a wall).
Generally we design things to expect a certain voltage and let the right amount of current through. Standard USB is 5V (always) and can go up to 2.1A.
Because of this design, the voltage has to match (at least within 0.5V or so) or otherwise something will blow up. The charger should be able to handle at least as much current as the device wants. With USB this is less of an issue because the device will charge slower if the charger can’t supply enough current. With older chargers it would overheat the charger.
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