Conventional Current and Electron Flow

You can’t see electricity, but you can notice it’s effects. So, it helps to visualize electric current/electrons flowing while you analyze, design, or build a circuit.

Current limiting resistor to protect LED basics diagram by electronzap electronzapdotcom
Current limiting resistor to protect LED basics diagram by electronzap electronzapdotcom
  • Conventional current. Imaginary fluid like substance moving from more positive to more negative.
  • Electron flow. Subatomic particles (electrons) that really exist and flow from negative to positive.
Conductive path for conventional current and electron flow illustrated by electronzap electronzapdotcom
Conductive path for conventional current and electron flow illustrated by electronzap electronzapdotcom
  • Yellow dots in the diagram above indicate moving charges. Either negatively charged electrons or imaginary positively charged current charge carriers.
    1. One way to imagine flow is that the simulated power source paddles rotating the positive charge carrier dots clockwise from positive, through the load (not illustrated above), and back to the negative side of the power supply. Don’t forget that in real circuits, you need components along that path in order to dissipate power.
      • Conventional current is typically imagined while designing or building a circuit due to it being how electricity was imagined before electrons were discovered in the early years of electronics study. Ground is usually considered 0V and typically assigned to the negative side of a single power supply. Single supplies are typically what is used to power DC circuits.
    2. Another way you can imagine flow is that the paddles push large batches (Coulombs) of electrons from the negative  supply, through the load (not illustrated above but needed in actual circuits), and back to the positive supply.
      • Atoms are really made of Protons and Electrons. So, although you can’t see them, it helps to understand how they interact with neighboring atoms in order to better understand the electrical properties of different materials. Especially semi conductive material.

Resistance:

Voltage pushing moving charges through a resistance visual diagram by electronzap
Voltage pushing moving charges through a resistance visual diagram by electronzap

Resistance limits current flow from a given voltage. Behaving much like how the size of a water pipe limits the amount of water that flows through it for a given pressure.

The relationship between voltage, current and resistance is linear. Twice the voltage across a given resistance, equals twice the current through that resistance.

  • 1 volt will push 1 amp of current through a resistance of 1 ohm. Don’t do that though unless it is at least rated to dissipate at least 2 watts!
  • 2V will push 2A of current through a resistance of 1Ω. Don’t do that though unless it is at least rated to dissipate at least 8 watts!
  • 1 volt will push 0.001 amp (1 milliamp) of current through a 1,000 ohm resistance.
  • 2V will push 0.002A (2mA) of current through a resistance of 1,000Ω.
Multimeter placement for measuring voltage resistance current schematic and Current Voltage IV linear relationship diagram by electronzap electronzapdotcom
Multimeter placement for measuring voltage resistance current schematic and Current Voltage IV linear relationship diagram by electronzap electronzapdotcom

The “friction” from current flowing through resistance creates heat. The heat, or power (P) in watts, produced by a component can be calculating by multiplying the volts across it, by the amps through it. P = VI. Always make sure a component is rated for at least twice as much wattage as it will be expected to dissipate.

Electron paths of conducting and insulating atoms with EMF applied diagram
Electron paths of conducting and insulating atoms with EMF applied diagram

It is more accurate to think of electrons as shown above.

  • Good conductors are made up of atoms with a single valence (outer most) electron. Since the valence electron is relatively far away from the atom nucleus, it can be moved to other atoms really easily.
  • Good insulators have a number of electrons in their valence (outer most) shell, and are therefore held more tightly by multiple protons in the nucleus.

Topics to be added:

  • Coulombs

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