The dissipation factor measures the inefficiency of a capacitor’s insulating material, with low dissipation indicating better efficiency. It is measured by testing the material between metal plates and without it, and is important to understand for specific electrical circuit applications. The dissipation factor is used in applications such as microwave cooking.
The dissipation factor is a measure of the inefficiency of a capacitor’s insulating material. It typically measures the heat that is lost when an insulator such as a dielectric is exposed to an alternating field of electricity. A capacitor generally has two metal plates and some sort of insulator in between. A ratio of the capacitance when there is an insulating material, to when the plates are separated by air or vacuum, is often referred to as the dielectric constant. The reciprocal of this ratio defines how the insulating material reacts and what its resistance is at a particular frequency, resulting in a value for the dielectric dissipation factor.
If a material has low dissipation, it generally means it has better efficiency. This characteristic is usually defined at a particular frequency. To measure the dissipation of a material, a test with the material between metal plates and then a test without it is typically done. The results can be expressed in a ratio, which is the dielectric constant typically used to test material dissipation. A dissipation factor test can be completed in other ways, such as using equipment such as test cells with different electrode configurations; the test method may vary depending on the application.
When a dielectric material is exposed to an electric field, its molecules rearrange themselves, which requires a significant amount of energy. After the field is removed, the energy cannot be recovered. The dissipation factor is often referred to as the power factor, especially when an alternating current is used with a capacitive circuit unaffected by resistance or induced current. A power factor of zero generally indicates that there is no dissipation. Power losses are usually calculated by multiplying the dissipation by the voltage and current.
The dissipation factor of air and vacuum is usually zero, although air generally has a small enough loss value to be discounted under most circumstances. This is measured for specific materials, such as polyester, at a particular frequency. Wherever a specific material is considered for use in an electrical circuit, it is generally important to understand what its energy loss is.
There are applications that often make use of the dissipation factor, such as the principle involved in microwave cooking of food. The alternating electric fields of a microwave oven cause energy losses from polarizing and depolarizing water molecules. This results in sufficient heat for the food to cook.
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