### Pages to are hidden for

```					  START        Daily Sprint
1. What is a resistor?

2. Name and describe the different types of
resistors.

3. Draw a circuit diagram with a DC source, a
photoresistor, and a motor.
MSA Problem
Sarah mixes salt and sugar together in a
small bowl. Which of the following
describes a property of the mixture?

A.   It is soluble in water.
B.   It is magnetic.
C.   It is metallic.
D.   It is liquid.
Quick Review
1. Diodes can be used to protect
electronic components from current
flowing in another direction. Describe
another application outside of
electronics where it would be important
for something to flow in only one
direction.
2. Describe three objects in your house
that utilize LEDs.
Quick Review
3. Use the Internet to research the use of
LED systems to replace general
household lighting. Describe one
replacing standard light bulbs with LED
lighting.
Resistance
Resistance
•   Resistance
•   Variable Resistors
•   Photoresistors
•   Fixed Resistors
•   Measuring Resistance
•   Resistance Color Codes

This presentation is intended to be used with Activity 4.2.3 Resistance.
Resistance
Resistance: The opposition of
current flow
Tank (Battery)                                                   Faucet (Switch)

Pipe (Wiring)

What happens to the flow (current) if a rock gets lodged in the pipe?

Flow (current) decreases
Resistance
The opposition of current flow
•As resistance increases, current decreases.
•All components and wires have some
resistance.
•Materials that are good conductors offer little
resistance.
Resistance
External factors that affect resistance include:

Thickness                                  Resistance

Diameter
Larger Diameter ------------- Less Resistance
Smaller Diameter ------------- More Resistance
Resistance
External factors that affect resistance include:

Resistance

Length
Longer ------------- More Resistance
Shorter ------------- Less Resistance
Resistance
External factors that affect resistance include:

Resistance

Temperature
Cooler ------------- Less Resistance
Hotter ------------- More Resistance
Variable Resistors
A resistor whose value can be varied
between its minimum and maximum values

Symbol for Circuit
Diagrams
Variable Resistors
In your engineering notebook, draw a circuit diagram using a DC source
that will power an LED and is controlled by a variable resistor.

Build the circuit you designed
•Did the light turn on?
•Was the LED turned in the                   DC

right direction?
•How did the LED behave
when everything was laid out
correctly?
Photoresistors
A light-sensitive device in which the internal
resistance changes with a change in light
intensity

Symbol for Circuit
Diagrams
Photoresistors
In your engineering notebook, draw a circuit diagram using a DC source
that will power an LED and is controlled by a photoresistor.

Build the circuit that you designed (you
may want to space the photoresistor far
from the LED).
•Cover and then use a flashlight to adjust
the amount of light reaching the
photoresistor.
•What is the relationship between
resistance and light levels of the
photoresistor?
Fixed Resistors
Resistors with a value that cannot be
changed

Symbol for Circuit
Diagrams
Fixed Resistors
In your engineering notebook, draw a circuit diagram using a DC source
that will power an LED and includes a fixed resistor.

Build the circuit as shown so that you can easily
insert various resistors.
•Use 5 different resistors. Place them in order
from most to least resistance.
•Remember that the higher the resistance, the
dimmer the light will be.
DC
• With your team, design a circuit where the
living room light will turn on when the front
door is kept closed.
• Innovate your circuit to include an override
switch that can turn off the light even when
the door is closed.

(Use correct symbols)
• With your team, design a circuit for a
garage door that when headlights shine on
the garage door the motor will run and
open the door.
• Innovate your circuit to include a push-
button switch that will also open the door
even when there are no headlights shining
on it.
(Use correct symbols)
Measuring Resistance
Ohm (Ω): The unit of measure of electrical
resistance

More Ohms = More Resistance = Less Current
Measuring Resistance
• Remove the resistor from the circuit.
• Touch the ends of the probe to the wires.
–    Go back one position and use that setting.

In your engineering notebook, record the
values for each of the resistors you
measured.

Did you have the resistors
in the right order?
Resistance Color Codes
1st Band    2nd Band    3rd Band   4th Band
1st Digit   2nd Digit   Number     Tolerance
of Zeros               Band 1    Band 2    Band 3   Band 4
Black    0           0
Orange     White    Brown     Gold
Brown    1           1           0
Red      2           2           00                      3          9        0       +/- 5%
Orange   3           3           000                              390 Ω +/- 5%
Yellow   4           4           0,000
Green    5           5           00,000
Blue     6           6           000,000
Violet   7           7
Band 1     Band 2   Band 3    Band 4
Gray     8           8
Red       Red     Orange    Gold
White    9           9
Gold                                        +/- 5%        2          2       000     +/- 5%
Silver                                      +/- 10%
22000 Ω +/- 5% or
22 KΩ +/- 5%
Complete the Resistance Color Codes
chart in Activity 6.2.3 Resistance.
Image Resources
Microsoft, Inc. (2009). Clip Art. Retrieved January 13, 2009, from
http://office.microsoft.com/en-us/clipart/default.aspx

```
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
 views: 38 posted: 11/3/2012 language: English pages: 23