Measurement of capacitance by reed switch.

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Physics Laboratory Report


The number and the name of the experiment:

Experiment 1- Measurement of capacitance by reed switch(TAS)
The date of experiment:19 / 5 / 08

Objectives

  • Use a reed switch to measure the capacitance of capacitors.

Apparatus

Theory

A  reed switch is a two-way switch controlled by a signal generator as shown in Fig. C1. It can be used to charge and discharge a capacitor by connecting it across a power supply(point B) and a micro ammeter (point C) alternatively. When the reed switch connects the capacitor (C) to a power supply (V), the capacitor charges and stores electric charges. A  few moments later, the reed switch connects the capacitor to a micro ammeter. The capacitor discharges in which the frequency () is the signal generator frequency.

When the switch touches B, the capacitor is charged to a potential differences V, which is recorded by the voltmeter. The charge on the capacitor is :

                                        

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When the switch is in contact with C, the capacitor discharges through the micro ammeter.

This process of charging and discharging occurs times per second. In each second, pulses of charge () flow through the micro ammeter. Hence, the current () through the micro ammeter is given by :

Procedures

1.  The circuit was connected as shown in the setup of the diagram. The resistance of the variable resistor was set at its maximum value. The reading of the voltmeter was recorded.

2.  The coil of the reed switch is connected to a signal ...

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