Resistance and Resistors George Simon Ohm Ohms law

Resistance and Resistors George Simon Ohm "Ohm's law" - the relationship that the current through most materials is directly proportional to the potential difference applied across the material. R=E/I Resistance – All objects which current flows through impart a hindrance to the electron flow. Measured in W (Ohms) The Formula symbol is R

Most objects can only handle a threshold amount of current before they overload Resistors – a Device with a known value of resistance. Used to control voltage and current. Fixed Resistors – Single value of resistance Three common types Carbon-composition Film Wire-wound

Carbon-composition Resistors – A Powdered carbon mixed with a glue-like binder. Which is inside a protective Epoxy housing. (Most common type) Film Resistor – High temp resistor which is made of a ceramic element that has a film of either carbon or metallic compound. `` Wire-Wound Resistor – Handles High heat – A core of ceramic is used and a resistance wire is wound around it. Then it is coated with a ceramic or enamel coating.

Power Rating – The value that is assigned to a resistor related To how much Wattage it can dissipate. Usually corresponds with its physical size. The larger the Resistor the higher its wattage value.

Variable resistors – Potentiometer or Rehostat – are able to change their values Potentiometer – Carbon film element Rehostat – Nickle-Chrome element wire