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Resistance PowerPoint and Exercise PowerPoint Presentation

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					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
• 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
   into the COM (Common)                        Readout
                                                                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 ()


   settings area.                               Positive Lead

                                                Negative Lead
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
• Ohm’s Law Answers



       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
• Multimeter and leads
• 1 – 470W resistor
• 1 – 1.0KW resistor
• 1 – 1.5KW resistor
• 1 – 1.0MW resistor
• Breadboard
• Breadboard wire pack (pre-trimmed wires for making connections
  on the breadboard)
• 6V battery pack (includes 4 – “AA” batteries)
                                                         Resistivity


Team Challenge

                           Bread Board Layout




    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.

10. Record your current measurement.
                                                          Resistivity



Observations and Analysis
• Were there slight differences in your measured values
  from your calculated 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
   your left hand.
5. Squeeze tightly, and note the resistance measurement
   on the readout.
6. Record your 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.
   Does your body conduct electricity?
   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?

				
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Description: Resistance PowerPoint and Exercise PowerPoint Presentation