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Basic Electron Flow

Atoms and their structure

Electronices RESISTANCE

- Opposition to electron flow. - The resistance in a metal conductor is directly proportional to the length and inversely proportional to the cross-sectional area. R=Resistance р=specific resistance l=length A=Cross-Sectional Area

-Resistance sounds like a bad thing but we tend to use it to our advantage in most circuits. -Resistance is measured in Ohms (Ω) - Increase in temperature will also increase resistance. DEFINED

THEORY Notice as the resistance increases the current decreases. Resistance Current Thus anytime current needs to be limited in a circuit, a resistor can be added.

RESISTORS Resistors are devices that turn electrical current into heat energy. This is valuable when we would like to limit current flow to another portion of a circuit. Fixed Resistors Potentiometers Schematics There are two main types of resistors, fixed and variable. The variable resistor may also be called a potentiometer. The schematic symbols for each type are on the right. The arrow is used to denote variable. How can we tell what the value is of a resister? There are two ways, measuring with a meter or on a fixed resistor you can read the color code. Turn the page to find out.

Resistance Color Code Fixed resistors use color bands to make it easy to read their resistance from any angle or position First Number Second Number Number of Zeros or if: Tolerance /Accuracy Gold - divide by 10 Silver - divide by 100

Black = 0 Brown = 1 Red = 2 Orange = 3 Yellow = 4 Green = 5 Blue = 6 Violet = 7 Gray = 8 White = 9 Third color band: gold = divide by 10 silver = divide by 100 Fourth color band: gold = 5 % =.05 silver = 10 % =.10 Use the accuracy band to determine the resistors acceptable range of resistance % Acceptable Range LowestHighest

OHMS Law

E=IRP=EI

Any arrangement of components that allows an electrical current to flow Basic Electrical Circuits

A Basic Circuit There is only one path for the electrons to flow Battery A Source Battery Lamp A LoadLamp Wire A ConductorWire SwitchA Control Switch

A Series Circuit Electrons can only flow along one path, and MUST go through each component before getting to the next one. Battery A Source Battery 2 Lamps A Load2 Lamps Wire A ConductorWire Switch A Control Switch

A Parallel Circuit Two or more components are connected so that current can flow to one of them WITHOUT going through another A Source Battery A Load3 Lamps A ConductorWire A Control Switch

A Series-Parallel Circuit A combination of components both in Series and in Parallel