#### Capacitance

3 Pages 632 Words

Introduction:

Capacitance is the amount of charge that a capacitor can store per unit of voltage across its plates or simply, the ability of a capacitor to store electrical charge. The basic formula used to find capacitance is charge (Q) divided by voltage (V). The unit for capacitance is the farad (f).

The first step of the experiment deals with capacitance in DC (direct current) circuits. The circuit must be wired with a 100kÙ resistor in series with a 10ìf capacitor. A switch with the characteristics of push-button normally open is then inserted into the circuit. An ammeter will be placed in series into the circuit along with a voltmeter placed across the capacitor. The DC power supply will generate 5 volts of electricity.

Next, capacitance will be tested using an AC (alternating current) circuit. The circuit used to test this will include a 22ìf capacitor and a miniature lamp. Twelve volts of electricity will be generated with the DC power supply initially. The power supply will be replaced with an AC unit after observations are made regarding the behavior of the lamp under DC conditions.

Next, the RC time constants will be determined. The time constant of a series RC circuit is a time interval that equals the product of the resistance and the capacitance. A circuit is assembled with a 470kÙ resistor in series a parallel combination of a switch and a 2.2ìf capacitor. A voltmeter will be placed across this resistor and the power supply generates 15 volts of electricity. The capacitor will then be charged and discharged to determine the RC time constant.

Conclusion:

The current peaks initially when voltage is applied to the DC circuit. This is because a capacitor acts as a short the instant that current begins to flow. The voltage at this point is zero but increases as the capacitor charges. As soon as the capacitor is fully charged, the current has decreased to zero and the voltage is equal to the ...