This document provides an introduction to resistors. It defines resistors as devices that maintain a constant relation between current flow and voltage. Resistors are used to step up or lower voltage at different points in a circuit and to transform current and voltage signals. Resistors are made from materials like carbon, metal film, and wire, which give each type different characteristics. Resistors have a tolerance rating and range in value from less than 1 ohm to over 1 million ohms, with suffixes indicating values above 1,000 ohms or 1 million ohms.

1. Introduction to Electronics:
Section One: Resistors
James Noll - Instructor

2. Resistors

Resistors are defined as: “A device used in electrical
circuits to maintain a constant relation between
current flow and voltage.”

Resistors are used to step up or lower the voltage at
different points in a circuit and to transform a
current signal into a voltage signal or vice versa,
among other uses. The electrical behavior of a
resistor obeys Ohm's law for a constant resistance

3. Resistors
The unit of measurement of a resistor is the “ohm”

Resistors are made of several types of materials
including carbon, metal film and wire. Each material
gives each type of resistor a certain “characteristic”.

For instance, carbon is a common resistor material
used for general purpose resistors. Metal Film is a
material that is used for precision resistors and is
more delicate than carbon. Wire is used for high
power, high current applications and is considered
heavy duty.

4. Resistors

Resistors are generally a “two-lead” device

Each resistor type has a “tolerance” or percentage
accuracy – 1%, 5%, 10%, 20%, etc.

Some resistors are color coded while others have
printed information on them. The color code will be
explained later.

Resistors are considered a passive device and are a
fixed value.

Potentiometers are a variable resistor.

5. Resistors

6. Resistors

Resistors have a wide range of values:
− Resistors range in value from less than 1 ohm to
over one million ohms.
− Each resistor has a “suffix” to indicate it's value
− For resistors less than one thousand, there is no
suffix.
− For resistors greater than one thousand, the suffix
is “K”
− For resistors greater than one million, the suffix is
“M”

7. Resistance Formulas

The basic formula for resistance is:
− R=E/I where R is resistance, E is
voltage and I is current.
− The formula is used in Direct
Current circuits only.