# Resistance PowerPoint and Exercise PowerPoint Presentation by MikeJenny

VIEWS: 112 PAGES: 20

• pg 1
```									Resistivity
Resistivity

Introduction

KWLD

• What do you know about resistance in
materials?

• What do you want to know about resistance
in materials?
Resistivity

Check it Out
Check out the multimeter

Materials
• Multimeter.
• 1 - 470 resistor
• 1 – 1.0K resistor
• 1 – 1.5K resistor
• 1 – 1.0M resistor
• Breadboard wire pack 6V battery pack
Resistivity

Check it Out
1. Plug the red (positive) lead
into the V
(Voltage/Resistance)
connection hole.                   Multimeter – Resistor Measurements
2. Plug the black (negative) lead
Volts DC        Volts AC

connection hole.                             Measurement
Range Dial      Amps               Ohms

3. Turn the measurement range                   Resistance
Current
10A
Resistance
mA COM V

dial into the resistance                     Settings ()

4. Set the range setting to a level
Resistor
higher than the resistance of
the resistor you will be
measuring.
Resistivity

Check it Out
5. Touch the red lead to one end of the resistor and the
black lead to the other end.
6. The readout will display the resistance value according
to the scale you set.
Resistivity

Check it Out
7. Record your actual measured resistance value for the
resistor and the corresponding “color bands” on the
resistor in the table in your Lab Journal.
8. Set these resistors aside, they will be used later.
9. Turn the measurement dial back to OFF when not in
use to conserve the battery.
Resistor   Actual measurement   Color bands

470
1.0K
1.5K
1.0M
Resistivity

Team Challenge
• Ohm’s law: V=I*R
• Use Ohm’s law to fill in the empty table cells in your Lab
Journal.
Resistivity

Team Challenge

Formula   Voltage   Current   Resistance
V=I*R       3.6     3.6mA       1.0K
I=V/R     9.0V      9.0A       1.0K
R=V/I     9.0V     3.6mA       2.5K
I=V/R     6.0V      3.0A       470
Resistivity

Team Challenge

Goal: experience the relationship is between voltage,
current, and resistance in an electronic circuit.

Materials List
• Calculator
• 1 – 470W resistor
• 1 – 1.0KW resistor
• 1 – 1.5KW resistor
• 1 – 1.0MW resistor
• Breadboard wire pack (pre-trimmed wires for making connections
• 6V battery pack (includes 4 – “AA” batteries)
Resistivity

Team Challenge

The holes in these columns are connected up & down

The holes in these rows are connected across
Resistivity

Team Challenge
1. Connect battery to the ends of the “+” and “-“ rows with
the red wire going to the “+” and the black wire going to
the “-“.
2. Place the 470 resistor with one end in a hole in one
column and the other end in a hole in another column.
3. Connect a small wire from a hole in the “+” row into a
hole corresponding to the column where one end of the
resistor is connected.
4. Connect a small wire from a hole in the “-” row into a
hole corresponding to the column where the other end
of the resistor is connected.
Resistivity

Team Challenge
5. The breadboard layout should          Resistor Circuit Layout
resemble the image at right.
• To measure the voltage across
the resistor use the following
setup and verify that the batteries
are producing approximately
-
6.0V. Be sure to set the                                              +
multimeter on the 20 setting in                           Battery   Red
the DC Voltage setup area so                              Battery
Black
Battery
that it will be able to measure                           Battery
6.0V without over-ranging.
• Record the voltage
measurement.
Resistivity

Team Challenge

Measure the current in the circuit
6. Insert the meter between the “+”
row and the upper side of the
resistor (remove the little wire that
was connecting this side of the
resistor to the “+” row).
Resistivity

Team Challenge
7. Verify that your current calculation was accurate.

8. Be sure to set the multimeter on the 20m setting in the
DC current setup area

9. Be sure that your red lead is connected to the “mA”
connection of the meter instead of the “V” connection.

Resistivity

Observations and Analysis
• Were there slight differences in your measured values

• Why or why not?

• Why did the buzzer get softer with increased
resistance?

• What is required to increase the buzzer sound?
Resistivity

Observations and Analysis
Can you see the relationship between
resistance, voltage, and current? (V=IR)
• For constant resistance, the relationship
between voltage and current look like the
plot in (a).                                (a)

• For constant current, the relationship
between voltage and resistance also
looks like (a).
• For constant voltage, the relationship
between current and resistance looks
like (b).
(b)
Resistivity

Conclusions

Finish the KWLD

• What did you learn about resistance in materials?

• What can you do with what you learned about
resistance in materials?
Resistivity

Make the Connection
1. Use your multimeter to measure the resistance of your
body from one hand to the other.
2. Set the meter to 20M.
3. Grab the tip of the red lead between two fingers in your
right hand.
4. Grab the tip of the black lead between two fingers in
5. Squeeze tightly, and note the resistance measurement
What factors do you think cause the variations
between the measurements of various people?
Resistivity

Make the Connection

5. Now lick the four fingers you used to get them wet and
repeat the measurement.
6. Record the new measurement.
How did licking your fingers affect the measurement?

Compare your measurements with others. How do the
measurements vary?
What factors do you think cause the variations
between the measurements of various people?
Resistivity

Make the Connection

• What affects the resistivity of various materials?

• How might doping can change the resistance of
materials?

```
To top