Parallel Plate Capacitor Lab Report

"ELECTRICAL AND ELECTRONICS ENGINEERING"
LABORATORY IV


"PARALLEL PLATE CAPACITOR"



Student's Name: Mahroo Uris
Student's ID: SCM-030782
Lecturer Name: IR Muhammad
Date of Experiment:19th March 2015
Date of Submission: 26th March 2015

Abstract:
In this experiment we are to verify the capacitor's dependence on plate size and the spacing between the two parallel plates of the capacitor. Also this experiment deals in the calculation of the value of capacitors.

Objective:
-To verify the dependence of capacitor on plate size and spacing for a parallel plate capacitor.
-To measure the capacitance of the capacitor.

Introduction:
A capacitor is a device that stores energy in the electric field created between a pair of conductors on which electric charges of equal magnitude but opposite sign have been placed so a capacitor can be made up of two metal surfaces separated by a certain distance. When there is a potential difference across the conductors, an electric field develops across the dielectric causing positive charge to collect on one plate and negative charge on the other plate. If battery has been attached to a sufficient amount of time no current can flow through the capacitor. However if a time varying voltage is applied to across the leads of the capacitor a displacement current can flow.
An ideal capacitor is characterized by a single constant value for its capacitance. Capacitance is expressed as the ratio of the electric charge Q on each conductor to the potential difference V between them. The SI unit for capacitance is Farad (F) which is equals to 1 Coulombs over 1 volt.
When two parallel plates are connected across the battery, the plates become charged and an electric field will be established between them. Using the definition of capacitance we can determine the capacitance C of an ideal capacitor as a function of its structure.

This equation for the capacitance of a parallel capacitor shows that C is a constant independent of the charge stored in on the plates or the voltage across the capacitor.
The amount of charge needed to produce a potential difference in the capacitor depends on area of the plates, distance between the plates and non conducting material between the plates.
Capacitors are widely used in electronic circuits for blocking direct current while allowing alternate current to pass.

Apparatus:

Parallel plate capacitor (need to make five different capacitors with Aluminum foil for each part of the experiment.
A stack of A4 paper.
Ruler.
Digital Multi meter.

Procedure:
PART A: To verify the dependence of capacitance on plate size for a parallel plate capacitor.
Took aluminum foil and cut them in rectangular shape in pairs and placed required number of paper between them. This arrangement now acted like a capacitor.
Made five such capacitors of different sizes. The thickness must be uniform and constant for all the capacitors.
Then measured the capacitance and the area of each capacitor. Recorded the data in Table 1.
Found the dielectric constant k, in each case.
Graph of Capacitance versus Area.
PART B: To verify the dependence of capacitance on spacing between the plates for a parallel plate capacitor.
Followed the first step of part A to make capacitor.
Made five capacitors of same area with different thickness. The number of the paper between the pates changes the thickness of the capacitor.
Then measured the capacitance and the thickness of each capacitor. Then recorded the data in Table 2.
Found the dielectric constant k in each case.
Graph of capacitance versus thickness.

Results:
Table 1
Spacing thickness between the plates = 2.5 meter
Area of the plate m2
Capacitance (Farad)
Dielectric constant k
2
7.1 x 10 (-12)
1.03
3
1.1 x 10 (-11)
1.00
4
1.4 x 10 (-11)
0.98
5
1.7 x 10 (-11)
0.96
6
2.1 x 10 (-11)
0.92


Table 2
Area of the plate : 5 meter square
Spacing thickness between the plates meter
Capacitance (Farad)
Dielectric constant k
2.5
1.8 x 10 (-11)
1.02
3.5
1.3 x 10 (-11)
1.03
4.5
9.8 x 10 (-12)
0.99
5.5
8.0 x 10 (-12)
0.99
6.5
6.8 x 10 (-12)
1.00


Discussion:
The relationship between the capacitance and the area of the plate in part A of the experiment. In part B of the experiment we were to see the relationship between the capacitance and the spacing between the two plates that is the distance between the two plates of the capacitor.
When part A of the experiment was carried out , the results were such that when the area of the plate was increased keeping in mind that the spacing between the plates was kept constant, the capacitance increased.
And in part B of the experiment when the spacing between the plates was increased, capacitance decreased keeping the area of the plate constant in this part of the experiment.
The dielectric constant was calculated using the formula by simply putting the values in the equation.

Conclusion:
After conducting the experiment, the conclusion is such that the objective of the experiment is achieved and the results are also verifying the theory which states that when the area of the plate is increased the capacitance is increased , that shows that area of the plate is directly proportional to the value of the capacitance.