The capacitance of capacitors is one of the fundamental values that are taken into account when calculating electrical circuits. This value for a flat capacitor is calculated by its geometric dimensions and the type of dielectric between the plates. The capacity of an arbitrary capacitor can be measured with a device or connected to an alternating current network.
Necessary
- - ruler;
- - vernier caliper;
- - table of dielectric constants of substances;
- - tester;
- - an alternating current source.
Instructions
Step 1
To find out the capacitance of a flat capacitor, determine the area of one of its plates. Do it geometrically by finding the area of a circle if it is round or the area of a square if it has that shape. Using a vernier caliper, measure the distance between the capacitor plates in meters. If there is air between the plates, then the dielectric constant of the medium is considered equal to 1.
Step 2
If there is another dielectric there, find out what kind of substance it is and find the dielectric constant from a special table. For example, for rubber this value is 7. Find out the capacitance of the capacitor C, for which multiply the dielectric constant ε by the electrical constant ε0 = 8, 85 • 10 ^ (- 12) and the area of the plate S in m², and divide the result by the distance between the plates d (C = ε ∙ ε0 ∙ S / d). The result will be obtained in Farads.
Step 3
Find out the capacitance of an arbitrary capacitor by measuring its capacitance in the AC circuit. This must be done if the electrical capacity is not indicated on its body. To do this, connect the capacitor to an AC source with a known frequency. For example, the frequency of the current in the household network is 50 Hz. After switching the tester to measure current, install it in series with the capacitor. Find the current value in amperes.
Step 4
Switch the tester to measure voltage and find its value on the capacitor plates. The measurement result should be in volts. Make sure that the active resistance of the circuit is negligible (except for the capacitor there should be no consumers), otherwise the data will be distorted.
Step 5
To find out the capacitance of the capacitor C, the current in the circuit I, divide sequentially by the number 2, the number π≈3, 14, the frequency of the current in the network f, and the voltage on the plates of the capacitor U (C = I / (2 ∙ π ∙ f ∙ U)).
Step 6
If the tester has a capacitance measurement function, use it. Switch the device to the electrical capacity measurement mode and connect to the capacitor plates.
