Voltage, Current and Resistance

Voltage:-

Force of attraction exists between a positive and negative charge.

Certain amount of energy must be exerted, in the form of work, to overcome the force and moves the charges a given distance apart. 

All opposite charges possess a certain potential energy because of the separation between them.

The difference in the potential energy per charge is the potential difference or voltage.  

Definition of voltage:-

V = W / Q

One volt is the potential difference (voltage) between two points when one joule of energy is used to move one coulomb of charge from one point to the other.

Current:-

Current (I) is the amount of charge (Q) that flows past a point in a unit of time (t).

I = Q / t

One ampere is a number of electrons having a total charge of 1 C move through a given cross section in 1 s. 

What is the current if 2 C passes a point in 5 s?      0.4 A

Resistance:-

Resistance is the opposition to current.

One ohm (1 W) is the resistance if one ampere (1 A) is in a material when one volt (1 V) is applied. 

Conductance is the reciprocal of resistance. 

G = 1 / R

Components designed to have a specific amount of resistance are called resistors.