Resistance

• • Types of electron flow. 


  Electron flow and Conventional flow
• Electron Flow


  Conceptually right since the flow of electrons are from negative to positive.
• Conventional Current/Flow


  The electrons flow from positive to negative.
• Current


  Any motion of charge from one region to another.
• Types of current.


  Direct Current and Alternating Current
• Direct Current


  One-directional flow of electric charge.
• Alternating Current


  Electric charges keep switching directions.
• Resistance 


  A force that counteracts the flow of current.
• Relationship between Current and Resistance


  Inversely proportional
• Resistivity


  Ratio of the magnitudes of electric filed and current.
• Resistivity depends...


  Type of material, size, shape, and temperature.
• Temperature Dependence of Resistance for Metals


  Temperature increases, the resistance increases
• When does superconductivity happen?


  At very low temperatures, resistance can become zero.
• Temperature Dependence of Resistance for Semiconductors


  As temperature increases, resistance decreases.
• Who discovered resistance


  Georg Simon Ohm
• Ohm's Law states...


  the relationship between voltage, current, and resistance in any DC circuit.
• Power


  Amount of energy that is absorbed or produced within the circuit.