The Difference Between Voltage and Current

Have you ever blown your breath onto a mirror and fogged it up?  The fog on a mirror is an accumulation of condensed water vapor.  The water vapor in our warm breath hits the cool mirror and condenses into water droplets.  Water droplets on the mirror do not flow from our mouth to the mirror.  The water droplets just appear on the mirror as a result of a flow of vapor from our mouth.  Water droplets (liquid) accumulate on the mirror as a result of water vapor (gas) from our breath moving to the mirror and accumulating on the mirror.  Now how does this compare to an electric circuit? 

 

Voltage does not flow.  Current flows in a circuit.  Current is the flow of electrons.  Voltage is an accumulation of charge particles.  Just like water vapor on a mirror, voltage appears as a negative potential when electrons accumulate somewhere.  When electrons moving in a circuit reach resistance, the electrons begin to gather up in front of the resistor waiting their turn to go through the resistance.  This bunching up of negative electrons causes a voltage to appear across the resistor.  The side of the resistor where the electrons are waiting to get through will have a negative potential with respect to the other end of the resistor.  As negative electrons gather up, they create a negative potential (voltage) just like water vapor condensing on a mirror forms water droplets. 

 

So, current flows and voltage appears across resistances in a circuit as long as current is flowing.  Voltage sources, like batteries, use chemical action inside them to separate electrons and protons to from a voltage.  Voltage sources do not require current flow to have a difference of potential (voltage).  Resistances will only have voltage across them if current is flowing through them. 

 

Voltage appears and current flows.  Just like water appears on a mirror when breath moves past the mirror.