I want to power my Arduino with a mobile charger, the out put is 5V 2A, will it kill my Arduino? And what's the max input current as power source?
"I want to power my arduino with mobile charger the out put is 5v 2apms will it kill my arduino?"
No! It won't. Even tough the reason has been already explained in this other post, I want to add something.
First of all, your question is really common among the ones who, like you (and me), have little/none electrical/electronic knowledge: if you ask such a question, it means you lack the "basic". This is perfectly ok, as we're here to learn "Arduino"... and this (typically) means we're here as the first step towards the electronic world. This is the very reason why I'm writing this answer. So... back to your question....
You're missing a key point, here: the maximum current that your power supply can provide.... is a maximum! And this does NOT means that such a maximum will be given always, and regardless of the devices connected to it!
In other words:
if you have a device that requires a very little amount of current to properly operate (as an example, this DHT22 sensor, requires as little as 2.5mA, or 0.0025 A) and connect it to your 2A power supply, what will happen is that along the wire from your power-supply to the DHT22 will flow only 0.0025 A of current;
if you have 100 (one hundred) DHT22 connected in some exoterical network/schematic, each one requiring 2.5mA of current, in order to power the all of them, concurrently, you need 2.5mA * 100 = 0,25A (or 250mA), that means that again, your power-supply, will be more than enough (to power the all of them, concurrently);
if you have 1000 (one thousand) DHT22, than you'll need 2,5A (or 2500 mA) and... if you need to power the all of them, concurrently, and if you need to stick with your power-supply (capable of "only" 2A)... you'll have problems, as your power supply will not be able to provide the amount of current required by your equipments (Which kind of problems you'll encounter is a matter for a different question!)
To be more specific:
- a common/base Arduino MEGA, without any external component connected, requires around 170mA of current;
- an common/base ethernet shield, requires 180mA of current;
So, if you plug your 2A power-supply to the USB socket of a MEGA which has an Ethernet shield mounted on its top, than your power-supply will have no problem at all in powering such two devices (as they jointly requires 350mA of current).
- you'll be able to power up to 6 of those MEGA+EthShield, as 6 x 350 = 1900mA, which is lower than 2A. Anyway, it's common practice to not require the maximum! It's good-style to not exceed 75/80% of the maximum, as sometimes, based on the quality of your power-supply, some "strange" things start happening when reaching the top!
In the above discussion we talked about "current", without taking into account the "voltage". Anyway, "voltage" is another key-point as "voltage" and "current" are strongly related.
In your OP you mentioned "mobile charger ... 5V" so I bet that you've an USB power-supply, rated at 2A/5V.
People starting playing with Arduino, should use such 5V power-supply to power Arduino trough the USB socket: it has been designed exactly to be connected to a 5V power source, being it an ad-hoc power-supply (with an USB termination) or an USB cable connected to a computer. As for this last case (a computer), please note that:
as for the USB2 specification, every USB2 "host" should be able to provide at least up to 500mA of current at 5V;
as for the USB3 specification, every USB3 "host" should be able to provide at least up to 900mA of current at 5V;
So, supposing you have an USB2 port on your PC and that you connect an USB "simple hub" (an hub without an explicit power-socket) to such port, you can connect only one MEGA+EthShield as this will require 350mA (of the 500mA available). If you have an USB3 port, you can connect 2 of them (and you can also try with three... but with unexpected results).
[...] The board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V, however, [...] the board may become unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts. [...]
The above statement introduce the "voltage regulator". This is another key-component that you should be familiar quite soon. At a very high-level, think to the "voltage regulator" as a magic box that:
from one side (the external world) receive a not-so-stable-and-clean current, flowing in the range 7V-12V;
apply some "magic" to such a current and bring it down _to_a_very_precise_ 5V flow;
provide the resulting 5V potential to the "internal world" of Arduino.
In other words, the voltage-regulator is responsable for providing the exact/constant 5V required by Arduino components, by relying on some "unstable" external current.
You might wonder how is possible to "lower" a 12V "input" to a 5V "output". I really don't know (and, actually, I don't care!). Anyway, a fundamental concept to be kept in mind is that such a reduction will produce "heat"! And the more you lower... the more heat it will produce! And the more current you'll "transform", the more "heat" it will produce! ...and if such heat will not be dissipated properly, chances are high that... something will stop working quite soon!
Having said all the above, please note that I'm well aware that lots of other concepts should have been discussed/introduced and that I have done some big oversimplification in the above description. Anyway, I really think that.... should someone had told me those concepts when I did my first steps in Arduino, my experience would have been shorter (...and easier). Nevertheless... don't blame me if you'll discover that those above will result mostly useless once you'll get slightly expert :-)