Circuits, Voltage & Current Electronics Mr. Engel

Objectives  Sketch a basic circuit and identify its four parts.  Explain differences between series, parallel and series-parallel circuits.  Define voltage and current.  Differentiate between direct current (DC) and alternating current (AC)  Explain what sine waves represent.

Parts of a Circuit  1) The Energy Source  2) The Conductors  3) The Load  4) The Control Device

Energy Source  Energy source produces the force to cause electrons to move.  The force is referred to as Voltage or Electromotive Force.  Common Energy Sources include chemical cells and electromechanical generators.  Current: the flow of electrons.  The current must remain continuous.

Conductors  Conductors provide an easy path for electron flow.  Copper is the most common conductor.  Insulators used to prevent shorts and accidents.  Other common conductors include your automobile frame and gold in circuit boards.

Load  Load changes the energy of moving electrons into some other useful form of energy.  Series Circuit: provides only one path or loop for electrons to move from source to load and back.  Parallel Circuit: two or more different paths or loops which electrons can flow.  Series-Parallel: Combination of series and parallel circuits to form one circuit with several paths or loops.

Circuits in Action  Simple light circuits 

Control Device  Control devices open and close the circuit, thus opening or closing the flow of electrons.  When a switch is “ON”, the circuit is complete and electrons can flow  When a switch is “OFF”, the circuit is broken and electrons are blocked from flowing  Other devices include: electromagnetic relays, diodes, transistors, and logic circuits.

Voltage  Most home electrical equipment:  120 Volts  Industrial applications:  120 V, 208 V, 480 V, 4160 V, higher  The Common Flashlight:  1.5 V  Some television picture tubes:  30,000 V

Current  Flow of electrons is measured in Amperes, or Amps  One amp = 6,240 Quadrillion electrons flowing past one point in one second of time  100 Watt Light Bulb = 0.8 A  1 HP Electric Motor = 6 A  Cranking of Car Motor = over 200 A

Direct Current (DC)  Produced in a circuit by a steady voltage source.  + and - terminals don’t change over time.  “Fixed Polarity”  Electric Cells, Batteries and DC Generators create a direct current.

Alternating Current (AC)  Produced by a voltage source that changes polarity (+ & -) with time.  Electron flow flows one way, then another, then back.  Alternators produce an alternating current.  Industrial induction motors use AC

Brain Boosters!  What items in your home might use DC? AC??  Chapter Review Questions  Electricity & Electronics – Red Text Book  Numbers 1-23 on page 66  Complete the sentences and drop box