1. Resistance, Resistors and Symbols
ELECTRONICS
Mr. Engel

2. Resistance: an opposing force between one thing and another
Resistance: an opposing force between one thing and another. In electronics, the property of a conductor that opposes the passage of current is resistance.
Electrons collide with other electrons and atoms.
Collisions reduce the electron flow through conductor.
Similar to water passing through a dirt/sand filled hose.
Resistance

3. The Ohm The basic unit of resistance is the ohm.
One ohm is the resistance that limits current to 1 A when 1 V is applied in a circuit.
The letter symbol for ohm is “R”
The Greek capital letter omega is used as an abbreviation
1,000 ohms can be written as 1 kΩ
1,000,000 can be written as 1 MΩ
The Ohm

4. Resistance in Conductors
Resistance of a conductor depends on four things:
The kind of metal from which it is made.
Compared to copper, silver has 94% as much resistance.
Compared to copper, pure aluminum has 170% as much.
Its temperature.
The hotter it gets, the higher its resistance.
Its length.
The longer it is, the more resistance.
Its cross-sectional area.
The larger its area, the LESS resistance.
Resistance in Conductors

5. Resistors Resistors are common parts in many circuits
They are used to control voltage and current
Prevents conductors from overheating and burning
Operate either as fixed resistors or variable resistors
Fixed resistors have a set resistance.
Variable resistors have an adjustable amount of resistance
Ten-valued color code used to identify resistance
Three-valued color code used to identify tolerance (+/-)
Resistors

6. Bill Brown Realized Only Yesterday, “Good Boys Value Good Work.”

8. Potentiometers are used to vary the value of voltage applied to a circuit.
An example of a variable resistor.
Input voltage is applied at terminals A and C
Output voltage is released though terminals B and C
Used in amplifiers, radios, TVs, other adjustment items.
Potentiometers

9. Rheostats Rheostats used to control higher currents.
Examples include lamp and motor circuits.
Similar to a potentiometer, but larger.
Due to carrying larger currents and giving off more heat.
A & C inputs
B & C outputs
Rheostats

10. Resistor Potentiometer Rheostat
Basic Circuit Symbols

11. Basic Circuit Symbols Battery Light-Emitting Diode
Wire Wires Joined Wires Not Joined
Basic Circuit Symbols

12. Name three items that have variable resistors in them at home, school or work.
Chapter Review Questions
Electricity & Electronics – Red Text Book
Numbers 1-26 on page 80
Complete the sentences and drop box
Brain Boosters!