What is the different between current (A) and voltage(V) ?

Ohm's law states that, in an electrical circuit, the current passing through a conductor is directly proportional to the potential difference applied across them provided all physical conditions are kept constant.


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A voltage source, V, drives an electric current, I , through resistor, R, the three quantities obeying Ohm's law: V = IR
In mathematical terms, this is written as:


圖片參考：http://upload.wikimedia.org/math/2/a/8/2a8eabc66c332d4f93c269082317d6f1.png
,
where I is the current, V is the potential difference, and R is a proportionality constant (for the circuit defined) called the resistance. The potential difference is also known as the voltage drop, and is sometimes denoted by E or U instead of V.
The SI unit of current is the ampere; that of potential difference is the volt; and that of resistance is the ohm, equal to one volt per ampere. The law is named after the physicist Georg Ohm, who published it in 1826.

1. Electric current messured by ammeter refers to a flow of positive charge in solid metals( ( but not in non-metallic conductors), like wires .
2. Voltage measured by volmeter refers to the voltage drop across a device . Voltage is the difference of electrical potential between two points of an electrical network .


Hope this helps