A minimal Arduino C/C++ sketch consist of only two functions:
setup(): This function is called once when a sketch starts after power-up or reset. It is used to initialize variables and pin modes, and to initialize any other libraries.
loop(): After setup() is called, this function is called repeatedly. It controls the board until it is powered off or is reset.
This program uses the functions pinMode(), digitalWrite(), and delay(), which are provided by the internal libraries included in the IDE environment.
Arduino boards are able to read analog or digital input signals from different sensors and turn it into an output such as activating a motor, turning LED on/off, connect to the cloud and many other actions.
V = I x R
Voltage => pressure of water
Ampere / Current => rate of water
Resistance => With of pipe
Another resistant example
Amp – an ampere is the unit for measuring electricity. The accepted standard unit used for measuring how fast an electric current flows is an example of an ampere.
Volt – the basic unit of electromotive force in the SI and MKS systems, equal to the electromotive force, or difference in potential, that causes a current of one ampere to flow through a conductor having a resistance of one ohm.
Watt – the basic unit of electric, mechanical, or thermal power in the SI and MKS systems, equal to one joule per second or 10 ergs per second (of a horsepower): for electric power it is equal to one volt-ampere.
The rate at which electricity flows is measured as an electric current. The pressure is the voltage. And as we said before the watts are the power the water could provide (like to a mill wheel). The watt is a measure of how much power is released each second.
Led is a small light bulb.
Arduino Board Description