1. Resistor

2. Potential Drop  Within a material there is a voltage drop associated with a field.  The material can be a weak conductor. Charges may flowCharges may flow Field and equipotentials existField and equipotentials exist  The material will have a current I and voltage drop V.  

3. Ohm’s Law  Many materials have a linear relationship between current and voltage.  This relationship is called Ohm’s law.

4. Resistance  The ratio of the change in voltage to the current is the resistance. Like resistance to water flow by stones  Resistance is measured in ohms (  ). 1  = 1 V/A v A PP d

5. Non-Ohmic  Some materials have non-linear relations between current and voltage. Non-ohmic materialsNon-ohmic materials Fluorescent and incandescent lampsFluorescent and incandescent lamps Diodes and transistorsDiodes and transistors

6. Resistor  Material can be fashioned to have a specific resistance. This is a resistorThis is a resistor  Resistors can be made from very long conductors. Wound wire in a coilWound wire in a coil Very preciseVery precise  Carbon composites make good resistors.  The symbol for a resistor is a zigzag line.  Like other electrical symbols the orientation doesn’t matter.

7. Resistivity  The resistance of a material depends on the shape. LengthLength Cross-sectional areaCross-sectional area  The resistivity (  ) is the material-dependent part of the resistance.  Resistivity also depends on temperature. next