Parallel Plate Capicitor Lab Report 95 % Essay, Research Paper

Parallel Plate Capacitor and Insulators

Different stuffs were placed in between the home bases of a parallel home base capacitance and the alteration in electrical capacity for each of the stuffs was tested utilizing a galvanometer. The consequences were studied to find the dielectric invariable for each of the dielectric stuffs and to find the permittivity of air.

By its ego, consequences show that the parallel home base capacitance? s electrical capacity is reciprocally relative to the distance between the home bases. This relationship was plotted on a graph. The incline of this graph determined the permittivity of air to be 2.04E-10 F/m

For each stuff the electrical capacity increased by a changeless factor, under a changeless electromotive force. This is known as the stuff? s dielectric invariable. The relationship between Capacitance versus the alteration in thickness of a certain type of paper was reciprocally relative. This relationship was graphed and utilizing its incline, the dielectric invariable for the paper was calculated to be. The dielectric invariable was besides calculated for both plastic and wood to be and severally.

This experiment concludes that the electrical capacity additions when the stuffs are placed in between the home bases of the parallel home base capacitance.

Introduction

Meter

ichael Faraday foremost conducted experimentation of Dielectrics. The SI unit the Farad, to denote 1 Coulomb per Volt ( C/V ) , was named after this scientist. Through his experiments on capacitances, he found that by make fulling the interior home bases of a capacitance with different sorts of stuffs, it increases the electrical capacity by a changeless factor, the dielectric invariable. Each stuff used in between the home bases ( including air ) has a dielectric invariable. Faraday besides discovered that insulators consequence the? interrupt down? electromotive force, the maximal possible difference that can be applied between the capacitance plates before the insulator interruptions down and organize a conducting way. . This experiment attempts to carry on an experiment similar to Faraday? s on the belongingss of insulators refering merely to alterations in electrical capacity.

Theory

To cipher some of information needed from the consequences, the experiment involved the following theory. The Capacitance ( C ) of the parallel home base capacitance can be calculated given by the country of the home bases, the separation ( vitamin D ) between the home bases and the permittivity of the stuff ( vitamin E ) between the home bases:

C = eA / 500 equation 1

The dielectric invariable ( K ) can be calculated, given the permittivity invariable of the insulator ( vitamin E ) and the permittivity of a vacuity ( e0 ) .

K = vitamin E / e0 equation 2

The dielectric invariable can besides be found given the measured electrical capacity ( C ) of the dielectric stuff with the electrical capacity of a vacuity ( C0 ) , by uniting equations 1 and 2:

K = C / C0 equation 3

The Capacitance ( C ) can be determined given the a charge in Coulombs, and Voltage from the power supply:

C = Q / V equation 4

Apparatus

Figure 1 describes how the setup for the experiment was set up. This involved a voltmeter, to mensurate the electromotive force being provided by the power supply with a double-pole-double throw switch. The burden in the circuit was a resistance with the opposition of 1 Mega Ohm. The sum of charge in C was measured utilizing a galvanometer. There were besides two capacitances used, one of known electrical capacity of 0.00948mF to cipher the sensitiveness of the galvanometer, and a parallel home base capacitance with a vernier graduated table used in experimenting with insulators.

EXPERIMENTAL METHOD, OBSERVATIONS & A ; RESULTS

Determining Galvanometer Sensitivity

In order to change over the mensural warp from the galvanometer into C, the sensitiveness of the galvanometer needed to be determined. This is done utilizing the capacitance of a known electrical capacity, it being 0.00948 medium frequency. The power being supplied is about 83V. After leting some clip for the capacitance to bear down, the throw switch turned off the power, doing the capacitance to dispatch. When this happens, the sum of warp shows on the galvanometer and is recorded. This is repeated about three times to acquire an mean warp of 4.9mm. Using equation 4, from the Capacitance and the known electromotive force, the sum of charge in C is determined and is so divided by the sum of warp recorded. The sensitiveness of the galvanometer calculated is 0.16 & # 215 ; 10-5 C/m The capacitance so is replaced with the parallel home base capacitance and is ready to carry on the undermentioned experiments.

Determining permittivity of Air

By happening the incline on a graph of the Capacitance versus the alteration in the opposite additive distance between the parallel home bases, and by finding the country of the home bases, the permittivity of the stuff between the home bases can be calculated utilizing equation 1.

A standard metric R

uler is used to mensurate the diameter of the home bases. The radius is so plugged into the country of a circle expression A=2pr2. The radius of the home base is 12.5cm and the country of the home bases calculated is 981.7cm2 or 9.81E-2m2

Knowing the sensitiveness of the galvanometer, it is now possible to utilize it to mensurate charge. At a possible difference of 202 Vs, the sum of warp caused by the capacitance discharge read on the galvanometer is recorded at bit by bit increasing separations, shown on the vernier graduated table. This is initiated by throwing the switch to the power supply off after leting the capacitance a minute to construct up charge. Table 1 shows the ascertained consequences of the experiment. The sum of discharge from the capacitance at each separation is so calculated by multiplying the warp by the sensitiveness of the galvanometer.

It appears that the relationship between the sum of electrical capacity and the separation distance is reciprocally relative. Graph 1 is based on this relationship where the sum of electrical capacity is against the opposite of the separation.

Using this incline and equation 1, the determined air permittivity is 2.04 & # 215 ; 10-4 F/m.

Determining dielectric invariable for Paper.

Finding the dielectric invariable for paper involves happening the permittivity of the paper, and so ciphering the dielectric changeless utilizing equation 2. The process is indistinguishable to the old, except sheets of paper occupy the infinite between the home bases. The thickness of each sheet of paper steps to be approximately 7mm or 7 ten 10-3 millimeter. The sum of discharge was measured for every extra sheet placed in between the capacitance plates until 6 sheets. The separation distance between the home bases equals the thickness of the paper stack. Table 2 shows the ascertained consequences from this experiment, including the deliberate discharge. The relationship of the discharge versus the opposite of the thickness of the stack ( or separation ) is plotted on graph 2.

Using the incline of this graph in equation 1 determines the paper? s permittivity to be. Using the paper? s permittivity and the permittivity of air ( for this experiment? s intent, the permittivity of air is near adequate to a vacuity? s ) in equation 3, the dielectric invariable for paper is calculated to be.

Dielectric invariables of other stuffs

A dielectric invariable for a certain stuff can be determined by happening the ratio of its electrical capacity to the electrical capacity of the capacitance without the stuff, but at the same separation.

The thickness of each stuff was measured, and the sum that felt sufficient to carry on the trial is recorded as the home base separation. For each stuff, the electromotive force is kept at a changeless 100V. The sum of discharge through the stuff is recorded, so once more without the stuff at the same separation distance. The ascertained consequences and deliberate charge is shown in table 3. Using equation 4, the electrical capacity for each case of the stuff is calculated. Then by utilizing the electrical capacity of each stuff in equation 3, the dielectric invariable is calculated.

AREAS OF EXPERIMENTAL ERROR

By far the most erroneous of all the processs necessary in all of the experiments above is the reading of the galvanometer. Having small experience with this device, it is hard to find the maximal swing on the metre, given merely an blink of an eye to capture the reading with the bare oculus.

This mistake explained above shows through out the experiment because most of the informations depends on the galvanometer readings. It is non possible to find a certain per centum of mistake in this regard.

The deliberate permittivity of air is besides really wrong. This experiment determined that the permittivity of air was 2.04 & # 215 ; 10-10 and the recognized value is around 8.85 & # 215 ; 10-12, which is really the permittivity of a vacuity but near to that of air. It is obvious that this is a immense mistake of 2205 % of from the recognized value! Beginnings of mistake may indicate once more to the reading of the galvanometer, but the mistake is more likely the cause of a computational mistake.

Besides a notable country of mistake is in the separations made. The separations may be excessively far than they should be made. Note that in happening the permittivity of air, which the separation distance jumped from 0.3 and 0.5 to 1.0 and 2.0. Possibly a more accurate reading could hold been made utilizing closer separations

Decision

Despite the hapless truth of this experiment, it has yielded some sound decisions. From the evident addition in electrical capacity as the separation between the home bases increased. This means that Capacitance is reciprocally relative to the separation distance. This experiment besides concludes that by busying the infinite between the home bases with some stuff, the electrical capacity additions. Besides that each sort of stuff increases the electrical capacity of the capacitance by a changeless factor. This is known as the dielectric invariable.

REFRENCES