Electric Fields Experiment

Name: Emily A. Gatlin Partner: Whitney H. Date Performed: 14-Jan-2000 Section 004; T.A. John Carruth

Electric Fields Experiment OBJECTIVES In order to understand the concept of an electric field, this lab teaches how to measure the electric field strength, strength

while gaining a conceptual hold on the relationships between electric field

and electric potential

. This experiment utilizes differing electrode configurations

and accomplishes electric field patterns by demonstrating them in an experiment. INTRODUCTION An electric field is any space that will exert force on a present test charge whose magnitude is shown with this equation: , where

force and q = magnitude of charge.

Electric fields are vector quantities that move in a particular direction, from positive charge to negative charge. Thus, electric fields are created within a space by producing charges of opposite signs that remain separated. Within this experiment, the electromagnetic field (EMF) is applied to two separate electrodes to create an electric field through the tap water medium in the glass tray. Another integral component to the calculations required within this experiment is Coulomb’s law. Coulomb’s Law allows the computation of the magnitude of the electric field, using the charge distributions present from the two separate electrodes placed within the conducting medium, in this case—tap water. However, these charge distributions are often difficult to measure, but using the relationship to the electric potential magnitude of the electric field

the electric potential

can be used to calculate the

is easily obtainable by using a probe

connected to a digital meter displaying the voltage. The electric potential

equal to the quotient of the work over the magnitude of the point

charge as follows: Ѵ= . Therefore, the relationship of the electric potential the electric field,

is shown below:

, to the magnitude of

Emily A. Gatlin

Hence, the electric field strength at a point is calculable with the potential difference between nearby points that lie along the same line in the direction of the electric field and dividing the distance between these two points. Procedure The apparatus of the experiment consisted of a glass tray with a small layer of tap water that had two fixed electrodes sitting inside of it that were hooked up to a power supply in order to create an electric field within the tap water. Under the glass tray was a coordinate system that allowed the plotting of data points as the varying voltages were obtained. The voltage was read using a voltmeter connected to a freely moving probe to collect the necessary data. In the first part of the experiment, the voltage readings were used to collect data for 1.0 volts, 2.0 volts, etc while the position of each reading was recorded on graph paper. In the second component of the experiment, the same apparatus was used with a change. The probes now stood ~8-cm apart on a line along the tray’s axis in order to create a point charge within the glass tray. The same experiment was now repeated with this set-up and the same voltage reading data was collected and plotted along a second graph.

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Emily A. Gatlin Data Experiment 1 Voltage X 1.0 0.4 1.0 0.4 1.0 0.3 1.0 0.2 1.0 0.3 1.0 0.2 2.0 0.6 2.0 1.0 2.0 0.9 2.0 0.8 2.0 0.9 3.0 1.9 3.0 1.9 3.0 1.6 4.0 2.8 4.0 3.0 4.0 2.9 4.0 2.9 4.0 2.9 5.0 4.0 5.0 3.9 5.0 3.8 5.0 3.7 6.0 4.7 6.0 4.8 6.0 4.8 6.0 4.9 7.0 6.0 7.0 6.0 7.0 5.9 7.0 5.8 8.0 7.0 8.0 7.1 8.0 7.0 9.0 8.0 9.0 8.1 9.0 8.0 9.0 8.9

Y 2.5 4.5 6.7 8.5 9.8 14.8 12.8 2.5 5.5 8.8 9.9 0.9 5.9 13.0 0.9 3.0 6.8 11.9 13.0 1.0 5.9 11.8 14.8 0.6 3.0 9.5 14.9 0.9 5.0 10.0 15.2 0.8 5.2 11.8 0.5 4.5 9.0 13.2

Experiment 2 Voltage X Y 1.0 3.0 8.9 1.0 5.0 8.0 1.0 3.0 7.0 1.0 2.4 8.0 2.0 3.0 7.7 2.0 3.8 8.0 2.0 3.0 7.0 2.0 2.8 8.0 3.0 3.0 9.0 3.0 4.3 8.0 3.0 3.0 6.0 3.0 2.0 8.0 4.0 4.8 8.0 4.0 3.0 9.0 4.0 2.0 6.0 4.0 1.8 8.0 4.0 1.8 8.7 5.0 2.5 9.0 5.0 5.0 6.5 5.0 1.1 8.0 5.0 2.0 9.0 6.0 0.5 7.8 6.0 3.0 10.0 6.0 0.5 7.8 6.0 4.0 4.0 6.0 6.0 8.0 7.0 0.0 8.5 7.0 1.0 9.5 7.0 3.0 10.0 7.0 6.0 8.0 7.0 5.5 6.0 8.0 2.1 1.0 8.0 13.8 0.9 8.0 7.0 10.0 8.0 0.0 11.0 9.0 2.5 12.0 9.0 12.0 8.0 9.0 15.0 5.0 9.0 5.0 3.0

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Experiment #1 A B C Experiment #2 A B C

DATA POINTS X 2 6 9 X 1 1 1

Y 9 9 9 Y 11 12 14

Emily A. Gatlin

Experiment 1 16.0 14.0 12.0 10.0 8.0 6.0 4.0 2.0 0.0

1.0 v 2.0 v 3.0 v A

B

4.0 v

C

5.0 v 7.0 v 8.0 v 0.0

2.0

4.0

6.0

8.0

10.0

Experiment #2

16.0

16.0

14.0

A

14.0

12.0

B C

12.0

10.0

10.0

8.0

8.0

6.0

6.0

4.0

4.0

2.0

2.0

0.0

0.0 0.0

5.0

10.0

15.0

Results To find the electric field, the difference in the electric potential was used.

Experiment #1:

Experiment #2:

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9.0 v

20.0

3.0 v 5.0 v 7.0 v 4.0 v 8.0 v 9.0 v

Emily A. Gatlin

The results show that it is expected that the electric field lines run perpendicular to the electric potential lines in experiment 1 that has a uniform electric field. Additionally, the data points along the electric field line show how the magnitude of the electric field is calculated from the electric potential. Experiment 2 demonstrated how the electric field lines shift with the electric potential when surrounding a point charge. The possibilities for error within this experiment are the possibility of a faulty voltmeter, inaccurate plotting of the data points, the potential for charge to be transferred by touch to the probe with the measuring probe, the evaporation of water and all other sources of human error could produce less reliable data. However, this lab demonstrated the concepts behind electric potential and the magnitude of an electric field. Conclusion This experiment adequately addressed the relationships between electric field magnitudes and electric potential. The experiment allowed computation of the electric field magnitude using the gathered data from the experiments. The experiment also showed how the different types of charges associated with the electric field produce very different electric field lines and electric potential lines. In the first experiment, the separate charge distribution produces a uniform electric field that has nearly straight vertical lines and the nearly straight perpendicular electric field lines associated with them. In contrast, the second experiment shows the circular pattern produced from a point charge by the electric potential lines. Thus, the electric field lines lie perpendicular to the electric potential lines radiate from the point charge—all around it. This lab clearly shows how the electric potential is a very applicable method to compute electric field magnitude.

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