as long as the voltage is the same, the current is equal to or greater than the original adapter, and the connector is the same the phone will be fine.
it will only draw as much as it needs, so a maximum of 0.7A from your 2A adapter.
Yup. Think of a 120V wall outlet.
That thing's tied to a 15A breaker, which is likely tied to a 200A+ breaker, which is tied to more power than you'd ever want to mess with. (And live.)
But I can plug one of those limelight nightlights into a 120VAC outlet, and despite having at least 15A available to it, it'll only take what it needs, which in the case of those nightlights, is going to be about 0.0003 amps.
More than you were looking for (simplified):
Voltage is a measure of how much electrons (or charges) "want" to move somewhere - potential.
Amperage is a measure of how
many electrons (or charges) are moving past a point - current.
Resistance is a measure of how much something resists current.
If you have a Thing® that has resistance, such as a power adapter, cellphone, or nightlight, and expose its terminals to a voltage, those motivated electrons in the power wires will try to push through the resistance of the Thing®. However, if it's a high resistance, only a small number of electrons will pass through, regardless of how many may be available.
So here's what you've got:
- A lot of electrons available. (15 amp capacity)
- They're motivated. (120 volts)
- There's a lot of resistance in their way. (low-power nightlight)
Result: Only about 0.0003 amps goes through the nightlight. The rest of the electrons in the wire just get to kind of sit back and take a break, because the 120 volts isn't strong enough to shove loads of electrons through the resistance that's in its way.
This here is a simplified calculation of it, but if you had 0.0003 amps from 120V, that's a resistance of 400,000 ohms.
If you wanted to force all 15 amps through that resistance, you'd need to get some seriously motivated electrons. 6,000,000 volts would be able to push 15 amps through 400,000 ohms. At least until something melts or spontaneously turns into a puff of plasma.
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