Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [dielectric]

A dielectric is an insulator that can be polarized by applying an electric field. A common example is the use of a dielectric within a capacitor between the metallic plates to increase the surface charge.

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How does the tester screwdriver work?

How does the tester screwdriver work? If I put the tester screwdriver inside the "hot wire" of an electrical socket, it lits up if I press my finger against the metal cap on top of the screwdriver. This happens also if I stand on a surface of…
John Donn
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Voltage required for a spark plug - dielectric constant of air

The dielectric constant of air is approximately 3 kV/mm. The typical space between car spark plugs is between 0.6 and 1.8 mm. By multiplying those numbers in mm by the dielectric constant of air, we figure that a spark plug would work for between…
William Garske
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What lubricant is suitable for switch contact?

I have this expensive DPDT switch (20A 250V 2hp) which the only problem is dirty encumbered inside. The encumbrance is made of carbonized material and some kind of wax and dirty electrical contacts. The contact poles are in good shape after a good…
Fred Cailloux
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What impact, if any, does the solder mask color have on the electrical and mechanical properties of a PCB

At my place of work, we use soldermask colors as a sort of poke-yoke for manufacturing purposes E.g. Technicians know that green pcb goes with green, blue pcb with blue, etc. This has lead to some ... esoteric color choices including matte white,…
crasic
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Measuring currents between 100pA to 100uA

I want to measure absortion/resorbtion currents of dielectric when applying 1000V, 1500V, 2000V. I have made a small currents measuring device using a LOG114: I use : LOG114 with 1uA reference current on input I1. The power supply for the LOG114…
Nedelcu Bogdan
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Pros and Cons of Types of "Dielectric Grease"

I have come across two different types of dielectric grease. One, the "usual" kind, is a silicone grease that has added insulators. Another, less common, is a hydrocarbon grease, typically polyalphaolefin (PAO) grease with silica additives. I…
Trashman
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Can I calculate minimum rise time of a transmission line if I know the length and the loss tangent?

Overview: I am trying to work out if it's possible to transmit my 1.2Gbps MIPI data down a 600mm long flexible PCB strip. Assuming I have the impedance correct, will the signal still be degraded by the loss tangent of the dielectric? Some…
Rocketmagnet
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How does selecting a higher permittivity substrate in patch antenna reduce its size?

By selecting a higher permittivity substrate do we reduce the height of the antenna or we reduce the length of the patch antenna? We cannot reduce the length of the antenna as it is dependent on the wavelength.
Mrunal Shinde
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What dielectric liquids can be used as coolants?

I've seen some interesting videos of people putting their computers in containers with sunflower oil, where they continue to work normal. Are there any other dielectric liquids that can be used to cool a technical device which is fully submerged in…
user1306322
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How come distilled water hasn't replaced transformer oil as a high voltage insulator?

I've noticed that distilled water has an extremely high dielectric straight (65-70 MV/m). With that considered, how come it isn't used in the place of transformer oil for 10-20 kV applications where the structure might not need to last multiple…
user154046
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High voltage dielectric breakdown & layering insulators

I’m going to use 230 kV as the reference voltage for the example below; I know if I put a piece of metal too close to a 230 kV source it will breakdown the air and jump to the piece of metal causing a visible spark, even if the piece of metal is…
Nick
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Confusion regarding effect of dielectrics on energy stored in a capacitor

If inserting a dielectric has the effect of reducing the magnitude of the electric field in a capacitor (holding all other variables constant), then why is the energy stored in a capacitor directly proportional to the relative permittivity of the…
user468756
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Confusion in understanding the relation between permittivity and capacitance

The insulating medium between the capacitor plates is called dielectric. This appears in the Coulomb's law: $$F = \frac{q_1 q_2}{4 \pi ɛ r^2}$$ ɛ is the "permittivity" constant which depends on the medium. This can be written as: ɛ = \$ɛ_0×ɛ_r\$…
user1245
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How does a dielectric alter the electric field?

My textbook is trying to explain why adding in a dielectric between two conductors causes a change in the field inside. They provide the following image: I don't understand how the second image is equal to the third image. Why does polarization and…
dfg
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Building a cheap and stable microwave network analyser or oscillator (2-5GHz)

I am interested in measuring the changing dielectric constant of a liquid as it undergoes a process. My background research of scientific articles shows that the 2-5GHz range provides the best contrast between the before and after dielectric…
ljbade
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