OHM’S LAW

An excellent analogy for the simplest of electrical circuits is the water in a hose connected to a pressure valve. Think of the electrons in the copper wire as the water in the hose, the pressure valve as the applied voltage, and the size of the hose as the factor that determines the resistance. If the pressure valve is closed, the water simply sits in the hose without motion, much like the electrons in a conductor without an applied voltage. When we open the pressure valve, water will flow through the hose much like the electrons in a copper wire when the
voltage is applied. 

Current is a reaction to the applied voltage and not the factor that gets the system in motion. The more the rate of water flow through the hose, just as applying a higher voltage to the same circuit will result in a higher current. Ohm’s law in honor of Georg Simon Ohm, clearly reveals that for a fixed resistance, the greater
the voltage (or pressure) across a resistor, the more the current, and the more the resistance for the same voltage, the less the current. In other words, the current is proportional to the applied voltage and inversely proportional to the resistance.

The current I of Eq. results from applying a dc supply of E volts across a network having a resistance R ohm.

Taken from : Introductory Circuit Analysis 10th Edition by Boylestad