Title: C2 Examining the capacitance of a capacitor

I. Target:

* To check into the element which affect the capacitance of any parallel-plate capacitor using a reed switch.

2. Apparatus

2. Reed Change

* Signal generator

* Capacitor China (1 pair)

* Polythene spacers

* Low voltage power supply

5. Voltmeter

* Variable resistance

* Light-beam galvanometer

2. CRO

* Standard mass (eg. 100g )

* Connecting potential clients

* Drawing board

2. Vernier disc brake calipes for testing thickness of spacer

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III.

Theory

A capacitor is a system which can shop charge. That consists of two sheets of conductor segregated by a coating of insulator called dielectric. The capacitance of a capacitor is defined as the charge placed per device potential big difference applied to the capacitor:

Inside the experiment, a reed move allows the capacitor being charged up and discharged speedily:

The reed switch contains three small metal whitening strips (F, And and K) inside a a glass capsule which is surrounded by a coil. F and K are made of metallic but In is non-magnetizable material. In normal condition, K (called the reed) is in connection with N. Every time a current moves through the coil, F and K turn into oppositely magnetized so that K is attracted towards F and makes contact with it. When the current declines, K springs back into contact with N.

If the frequency from which the reed switch functions is farrenheit, the charging and discharging process will be repeated farreneheit times per second, as well as the charge Q on the capacitor is brought to the microammeter at the same rate.

The capacitor is definitely fully charged up and dismissed every time, the whole quantity of impose passes through the microammeter in a second is:

Q=CVf

This provides the size of theoretical current I actually.

The capacitance of the capacitor can be believed from

Hence, the reading in the microammeter displays the capacitance of the parallel-plate capacitor.

For the pair of plates are oppositely charged and arranged so they really are parallel to

one another and only a small length apart, then this electric field between them will be uniform apart from at their very own edges. In the event the edge effect is ignored the value of the

electric field strength between your plates is

Since the field is standard, we likewise have

Equating both of these values of E gives

So

Thus giving the capacitance of the parallel plate capacitor, C, to become

Since capacitance is defined as C =Q/V, the charge on a capacitor is definitely directly proportional to the potential difference from which the capacitor is recharged. The chart of charge Q against potential difference V shows the slope addressing the capacitance of a parallel-plate capacitor.

4.

Technique

1 . The galvanometer was set to the shorted location and the light sport was moved to off-set zero. The sensitivity of was established at X1. 0 and it was documented 2 . The circuit was connected as shown. A drawing table was added to the counter and the parallel plate capacitor horizontally was put on best. The capacitor plates with 4 polythene spacers located at the sides 3. The frequency and voltage from the signal electrical generator was modified such that a sound was heard and the spot on the light-beam galvanometer was deflected 4. Lab coats

five. A variable resistor was connected in series with the galvanometer to shield it from damage, which can result from an accidental connection of the m. c. supply to the galvanometer. 6. A CRO was connected through the variable resistance to monitor the discharging current pulse. The variable resistor was tweaked to a optimum value so that zero was reached by simply each pulse before the next one. A) Charge and applied s. d.

1 . The signal generator was set to the...