ANALYSIS OF DATA I
INTRODUCTION An electric field exerts a force on other electrically charged objects and is defined as the electric force
per unit charge. It is a region where electrostatic force is present and can be represented by electric field lines which are sometimes called the force lines. The electric field is outward from a positive charge and in toward a negative point charge. Equipotential lines are like contour lines on a map which trace lines of equal altitude. In this case, the altitude is the electric potential or voltage. They are always perpendicular to the electric field. The purpose of conducting this experiment is to study the nature of electric fields by mapping the equipotential lines and then drawing in the electric lines of force. This experiment wants the students to know the principle about electric field and equipotential lines. The equipotential line is mapped using a digital multi-meter to locate point with equal potential. In order to attain the objective stated above, it is important to locate the points as accurately as possible. The experiment is divided into two parts: a.) dipoles of unlike charges and b.) point source and guard ring. This experiment uses conductive paper as an electric field and a silver ink pen used to mark the electrodes. As a conclusion, the closer the lines are, the stronger the force acts on an object. If the lines are farther from each other, the strength of force acting on an object is weaker.
II
THEORY
The electrical field force acts between two charges, in the same way that the gravitation field force acts between two masses. An electric field surrounds electrically charged particles and time-varying magnetic fields. It exerts a force on other electrically charged objects. The electric field from any number of point charges can be obtained from a vector sum of the individual fields. A positive number is taken to be an outward field while the field of a negative charge is toward it. The electric field intensity is defined as the force per unit positive charge which would be experienced by a stationary point charge, or test charge, at a given location in the field by using the Coulomb’s law: (
)
Where: F - electric force experienced by the test particle
q - charge of the test particle in the electric field E - electric field wherein the particle is located. The equation give above, however, cannot be used for the computation of the experiment because we only need to plot the equipotential lines and draw the electric lines of force. This can be done by getting the coordinate for the same voltage for 8 trials.
1 Department of Physics Experiment 304 : Electric fields and Equipotential Lines– Analysis of Data
The objective of this experiment is to study the nature of electric field by mapping the equipotential lines and then drawing in the electric lines of force. It is important to conduct this experiment because the student will be able to know the principle of electric fields and equipotential lines. The electric field lines can be drawn using field lines which are called as force lines. Electric field lines are drawn such that a tangent to the line at a particular point in space gives the direction of the electrical force on a small positive test charge placed at the point. The reason why field lines are drawn is to show the direction and strength of the field. The direction of the electric field is always directed in the direction that a positive test charge would be pushed or pulled if placed in the space surrounding the source charge. An illustration below shows an electric field lines:
This illustration shows a positive charge electric field. It signifies that the field lines are originated from the positive charge.
This illustration shows a negative charge electric field. It signifies that the field lines end up at the negative charge.
Figure 1 – Field lines that originated from positive and negative charges formed an electric field
A positive charge exerts out and a negative charge exerts in equally to all directions. Thus, it is symmetric. The density of electric field lines indicates the strength of the electric force experienced by the test particle in a particular region. Thus, the closer the lines are, the stronger the force acts on an object. If the lines are farther from each other, the strength of force acting on an object is weaker. Equipotential lines are like contour lines on a map in which trace lines are of equal altitude. The altitude in this case is the electric potential or voltage. Equipotential lines are always perpendicular to the electric field. Each equipotential line is specified by the same single value of the voltage that all its points have with respect to its conductor.
The illustration shows equipotential lines of a dipole. The electric potential of a dipole show mirror symmetry about the center point of the dipole. Electric potential are everywhere that is perpendicular to the electric field lines.
The illustration shows equipotential lines of a point charge. The equipotential lines are circles and a sphere centered on the charge is an equipotential surface.
Figure 2 – Equipotential lines of a dipole and a point charge Note: Dashed lines are equipotential lines while solid lines represent electric field lines.
2 Department of Physics Experiment 304 : Electric fields and Equipotential Lines– Analysis of Data
III
MATERIALS USED
MATERIALS USED 2 pc 1 pc 10 pc 1 pc 1 pc 1 pc 1 pc 2 pc
conductive paper silver ink pen push pins circular template corkboard surface battery digital multi-meter connecting wires
Figure 3 – Materials used for the whole experiment
The set up was easy because we all followed the procedure properly. The only problem in this experiment is that it takes a long time to map out the location of the equipotential points. It was easy to choose a reading using a digital multi-meter, we chose a reading that didn’t have much decimal places so that it will not be hard to find the similar ones. Still, it took time in getting those points because the digital multi-meter’s reading is not stable and the value is always going up and down. As for the result, the points were connected and we projected the curve to all the quadrants.
IV 1.
V
OBJECTIVES
To study the nature of electric fields by mapping the equipotential lines and then drawing in the electric lines of force
DATA AND OBSERVATIONS
Equipotential lines are like contour lines on a map which trace lines of equal altitude. In this case, the altitude is the electric potential or voltage. They are always perpendicular to the electric field. The purpose of conducting this experiment is to study the nature of electric fields by mapping the equipotential lines and then drawing in the electric lines of force. This experiment wants the students to know the principle about electric field and equipotential lines. The equipotential line is mapped using a digital multi-meter to locate point with equal potential. In order to attain the objective stated above, it is important to locate the points as accurately as possible.
3 Department of Physics Experiment 304 : Electric fields and Equipotential Lines– Analysis of Data
The experiment is all about electric fields and equipotential lines and the problem that we are trying to solve here (in part A & B) is getting the voltages and the 8 coordinates (in each voltage) in order to get the graph of dipoles of unlike charges and a point source and a guard ring. A conductive paper is used for the set-up of electric field. A silver ink pen is used to mark the electrodes. The 10 pieces push pins are used to secure the conductive paper and the pushed pins that were pinned on the 2 marked coordinates serves as the electrodes. Also, the digital multimeter is used to determine its voltage. Table 1 – Dipoles of Unlike Charges Multimeter Reading 4.5 volts
3.7 volts
3.3 volts
4.1 volts
3.9 volts
Coordinates(x,y) 7 7 7.5 7 2.2 4 6 9.5 6 9.5 2 2 2.5 2 -7 -7 -7.5 -4 0 -8.5 -9.5 -6
0 -1.5 -2.2 1.5 7.5 0 -8.5 -9.5 8.5 9.5 0 -5 -9.5 5 0 -1.5 -2.2 0 -4 -6 -9.5 8.5
Figure 4 : Resulting Graph of Dipoles of Unlike Charges
Analyzing the obtained data and results in part A, the lines which were connected by the dots shown in Figure 4 are the equipotential lines. On the other hand, the lines which have an arrow are the electric field. The positive charge is present on the left side of the figure while the negative charge is present on the right side of the figure. Table 2 – Point Source & Guard Ring Multimeter Reading 3.7 volts
3.5 volts
3.3 volts
3 volts
2.6 volts
Coordinates(x,y) 6 -6 0 0 5 -5 0 0 4 -4 0 0 3 -3 0 0 2 -2 0 0
0 0 6 -6 0 0 5 -5 0 0 4 -4 0 0 3 -3 0 0 2 -2
Figure 5 : Resulting Graph of Point Source & Guard Ring
In addition, the electric field lines were obtained through the concept of electric field which is perpendicular to the equipotential lines. The electric field travels from the positive charge on a perpendicular path with the equipotential lines towards the negative charge.
4 Department of Physics Experiment 304 : Electric fields and Equipotential Lines– Analysis of Data
CONCLUSION Upon carefully doing the necessary procedures of the experiment and by interpreting the obtained data and results, the primary aim of this experiment were achieved. And that is to study the nature of electric fields by mapping the equipotential lines and then drawing in the electric lines of force. In this experiment, electric field lines are drawn such that a tangent to the line at a particular point in space gives the direction of the electrical force on a small positive test charge placed at the point. The reason why field lines are drawn is to show the direction and strength of the field. The direction of the electric field is always directed in the direction that a positive test charge would be pushed or pulled if placed in the space surrounding the source charge. A positive charge exerts out and a negative charge exerts in equally to all directions. Thus, it is symmetric. The density of electric field lines indicates the strength of the electric force experienced by the test particle in a particular region. Thus, the closer the lines are, the stronger the force acts on an object. If the lines are farther from each other, the strength of force acting on an object is weaker. To simplify, the closer the lines are, the stronger the force acts on an object. If the lines are farther from each other, the strength of force acting on an object is weaker. Also, we used the conductive paper as the electric field, plotted equipotential points in it, and the resulting figure was a parabola. We plotted the same coordinates on the negative x-axis. After doing five trials, we connected the five parabolas with a line intersecting perpendicularly. This is the electric line of force with direction from the positive to negative x-axis. Another thing is that, we also plotted points surrounding the guarded ring. Using the origin as our point source, we produced circles. This means that the electric lines are trapped inside the guard ring. The reason for this is that the guard ring can conduct electricity since it is made up silver. This states that as the electric field lines increases its distance from each other, the strength of force acting on an object becomes weaker. As a conclusion, we can greatly see that the equipotential lines generated are proportional in strength with respect to their distances from the point source, from this we can assume that the strength of the electric charge is proportional to its distance.
5 Department of Physics Experiment 304 : Electric fields and Equipotential Lines– Analysis of Data
