Energy, power and resistance

• electromotive force (emf) is the work done on (energy gained) each unit of charge moving through a cell or battery
• An ohmic conductor is a conductor which obeys ohms law.
• Ohms law states that the current in an ohmic conductor is directly proportionate to the potential difference
• Potential difference is the work done (energy lost) per unit charge, the difference in potential between two points
• Voltage is the energy transferred per coulomb across a resistance
• Equation for energy transferred:

  $W =$$VQ$
• Energy transferred = eV = 1/2mv^2
• Resistance is how difficult it is for current to flow through a circuit.

  Equation:

  $R=$$V/I$
• Filament lamp:

  
• Diode:

  
• A Light Dependent Resistor (LDR) is a semiconductor that is sensitive to light, as light intensity increases the resistance decreases
• Thermistor works as the temperature increases, the resistance decreases
• Resistivity is a property of a metal which shows how easy or difficult it is for current to flow in the material.

  Equation:

  $p =$$RA/L$
• Power is the rate of energy transfer, measured in watts
• Equation for Power:

  $P =$$VI$