Unit 14 Lab
Honors/Academic Physics
Mr. Helzer
Name___________________ Number___________________
Electric Fields and Equipotential Lines\Surfaces
Directions: Read this entire lab before you begin. Follow the directions given on this lab. If you ask
your instructor a question that is answered on this lab already, then you will receive a reduction in your
lab grade.
Objectives:
1. The student will learn how to use a digital multimeter in order to map the Equipotential Lines (Equal
Voltage Lines) about a number of electrically charged geometric arrangements.
2. The student will learn how to use a digital multimeter in order to map the Electric Field Lines
between electrically charged geometric arrangements.
3. The student will learn how to use a digital multimeter in order to determine the direction of the
Electric Field Lines between electrically charged geometric arrangements.
Equipment Needed: Multi-meter with probes, DC Power Supply with red and black connection cables,
Electric Field and Equipotential Line Mapper Kit, graph paper, and a Digital Multimeter Meter.
Special Notice: Throughout this lab, you will need to refer to the following Power Point presentation K:\Helzer\Unit 14 - Electric Fields\ Unit 14 Electric Fields. This presentation will provide you with
assistance in setting up your experiment. Open this presentation now and save it in your applications
drive.
1. Begin by viewing the first six slides of the presentation and learning how to use the Digital Volt
Meter to measure voltage across a distance.
2. Get to know your multimeter. There are two different models in use. Which meter do you have?
Model 2704C
Model 2706 B
Other ____________
3. Refer to the slides labeled as “Procedure 1: Multimeter/Probes.” If you circled the meter model on
the left, then always view the dial position and probe connections for the meter on the left side of the
slides. If you circled the meter model on the right, then always view the dial position and probe
connections for the meter on the right side of the slides. Do not incorrectly connect the probes on the
multimeters. We will be using the DC side of the meter. Note the switch positions for DC voltage.
Insert the probes into the positions shown for your multimeter.
4. Refer to the slide labeled as “Procedure 1: Voltage Measurement.” Set the multimeter dial to the 20
V position.
Procedure 1: Equipotential Surfaces/Lines about an Electric Dipole
Note: If you are unsure of the directions below after you have read them, then ask you instructor
for clarification. Do not energize the DC Power supply until your instructor has approved your
experimental setup. Do not puncture the conductive paper with the multimeter probes.
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Unit 4 Lab
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1. Place the pre-drawn conducting paper onto the cork board. Insert metal push pins into the silver
conducting ink near the positions indicated on the slide labeled as “Procedure 1 – Equipotential
Surfaces/Lines.” If there is already a hole in the paper in the proper position, then place the pin in the
same hole.
2. On a separate sheet of graph paper, draw dots representing points B and C. Your scale on the graph
paper should be two blocks equals to 1.0 cm. The small squares of the conductive paper are 1.0 cm by
1.0 cm.
3. Refer to the slide labeled as “Procedure 1 - Plotting Equipotential Lines/Surfaces.” Connect the red
connection cable to the red plug on the DC side of the power supply, and connect the black connection
cable to the black plug on the DC side of the power supply. Connect the other ends of the connection
cables to the metal push pins located at points B and C as shown on the slide. Call for your instructor to
approve your setup.
4. Your instructor will energize your power supply and set the DC voltage to 10.0 Volts.
5. Use the multimeter to determine the actual voltage between the pins by placing the black probe on
the pin connected to point B and the red probe to the pin at point C. Read the voltage from the meter. If
it is not at 10.0 V, then, using slow steady turns, adjust the AC/DC Voltage until your meter reads 10.0
V between the pins.
6. Refer to the slide labeled as “Procedure 1 - Plotting Equipotential Lines/Surfaces.” Keeping the
black probe at point B, slide the red probe from point B straight towards point C until the meter reads
3.0 V. Using the grid lines on the conductive paper, determine the coordinates of the red probe’s
position. Plot this point on the graph paper provided. Do not write on the conductive paper.
7. Reposition the red probe as shown on the slide labeled as “Procedure 1 - Plotting Equipotential
Lines/Surfaces.” Slide the red probe back toward point B and then back outward from point B in a
different direction until the meter again reads 3.0 V. Use the grid lines on the conductive paper and
determine the coordinates of the red probe’s position. Plot this point on the graph paper provided.
Repeat this step until you have at least six points around point B on your graph paper. Do not go
outside of the solid grey, rectangular boundary around points B and C. Once you have six points,
connect the dots in order to form your 3.0 V equipotential surface/line.
8. Repeat step 5 in order to make sure that the voltage is still 10.0 volts between the probes.
Afterwards, repeat steps 6 and 7 for 4.0 volts and 5.0 volts. Repeat step 5 after each voltage
measurement.
9. Next, place the red probe at point C. Repeat steps 5 – 8. Switch “Red” with “Black” and “B” with
“C” when reading the directions in steps 6 – 8.
Procedure 2: Electric Field Lines between an Electric Dipole
Note: If you are unsure of the directions below after you have read them, then ask you instructor
for clarification. Do not puncture the conductive paper with the multimeter probes.
1. Using a large rubber band, lash the two probes together as shown in the slide labeled as “Procedure 2
- Plotting Electric Fields.” Note the positions of points a – e. These will be your starting positions for
the five electric field lines you will be drawing during this experiment.
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2. For this experiment, the black probe will function as the pivot as shown on the slide labeled as
“Procedure 2 - Plotting Electric Fields.” Position this probe at point b as shown. Pivot the red probe
around the black probe until the multimeter gives the highest reading for the electrical potential
(voltage). Plot this point on the graph paper provided on the same graph you used for Procedure 1. Do
not write on the conductive paper.
3. Reposition your probes so that the black pivot probe is on the coordinates from part 2. Pivot the red
probe around the black probe until the multimeter gives the highest reading for the electrical potential
(voltage). Plot this point on the graph paper provided on the same graph you used for Procedure 1.
4. Repeat step three until the electric field line reaches point C (you may not need all 10 rows in Table
2). Once you reach Point C, reposition the black probe at points a, c, d, and e. Afterwards, repeat steps
2 and 3 for each new starting point. Do not go outside of the solid grey, rectangular boundary around
points B and C.
5. Connect the points for each starting position. Be sure to indicate the direction of the electric field in
your graph. You have now traced out some of the electric field lines for an electric dipole.
Procedure 3: Parallel Plate Capacitor – Electric Field and Equipotential Lines
1. Refer to the slide labeled as “Procedure 3 – Parallel Plate Capacitor.” Connect Point H to the black
cord and point I to the red cord. Use the multimeter to determine the actual voltage between the pins by
placing the black probe on the pin connected to point H and the red probe to the pin at point I. Read the
voltage from the meter. If it is not at 10.0 V, then, using slow steady turns, adjust the AC/DC Voltage
until your meter reads 10.0 V between the pins.
2. On the graph paper provided, write points a – d on as shown on the slide labeled as “Procedure 3 –
Parallel Plate Capacitor.”
3. Keep the black probe on the pin at point H on the negatively charged capacitor plate. Move the red
probe along the line through point a towards the positively charged capacitor plate until the digital
multimeter reads 2.0 v. Immediately plot these coordinates on the second sheet of graph paper. You do
not have to record these coordinates.
4. Starting at point b, again move the red probe from the negatively charged plate toward the positively
charged plate until the meter again reads 2.0 V. Plot this point on your graph paper.
5. Repeat steps 3 and 4 for points c – d and plot these points. Connect these points for the 2.0 V
measurement.
6. Use the multimeter to determine the actual voltage between the pins by placing the black probe on
the pin connected to point H and the red probe to the pin at point I. Read the voltage from the meter. If
it is not at 10.0 V, then, using slow steady turns, adjust the AC/DC Voltage until your meter reads 10.0
V between the pins. Repeat steps 3 – 5 substituting 4.0 V, 6.0 V, and 8.0 V.
7. What types of lines did you just finish plotting? ________________________________________
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8. Using a large rubber band, lash the two probes together. Position the probes at point a with the black
probe on point a. Pivot the red probe around the black probe until the multimeter gives the highest
reading for the electrical potential (voltage). Plot the coordinates of the red probe on your graph paper.
9. Reposition your probes so that the black pivot probe is on the coordinates from part 8. Pivot the red
probe around the black probe until the multimeter gives the highest reading for the electrical potential.
Plot the coordinates of the red probe on your graph paper. Continue this process until the red probe
reaches the positively charged plate. Connect your points between the two plates of the capacitor. Be
sure to indicate the direction of the electric field in your graph.
10. Repeat steps 8 and 9 starting at points b – d.
11. What kind of lines did you just finish plotting? __________________________________________
12. If you were an electron placed next to the electrode labeled as H, then in what direction would you
move? Explain your answer.
Summary Questions:
1. Label the electric field lines in the figure to the right.
e-
2. Label the electric potential lines in the figure to the right.
3. Which end of the figure (right or left) would be positively charged? Negatively charged?
4. In which direction would the electron in the figure to the right move? Explain your answer.
5. True or False? Electrons move from areas of higher electric potential (voltage) to areas of lower
electrical potential (voltage). Explain your answer.
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1. Label the charges to the right
as either “+” or “-” and explain
why you labeled them as you
did.
2. Something is wrong with the picture to the left. What is wrong? Explain your answer.
3. Fill in the magnitudes of the charges below that would result in the electric field patterns shown.
Note the direction of the field lines. Explain your answer.
EIMASES © 2001-2007 Mr. Shannon W. Helzer. All rights reserved.
Unit 4 Lab
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