science

Vacuum variable capacitor

Vacuum variable capacitor is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Vacuum variable capacitor rather than just read about it. In short: A vacuum variable capacitor is a variable capacitor which uses a high vacuum as the dielectric instead of air or other insulating material. This allows for a higher voltage rating than an air dielectric using a smaller total volume.

Key takeaways

Vacuum variable capacitor belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Vacuum variable capacitor to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Vacuum variable capacitor from memory before moving on to harder problems.

Reference excerpt

A vacuum variable capacitor is a variable capacitor which uses a high vacuum as the dielectric instead of air or other insulating material. This allows for a higher voltage rating than an air dielectric using a smaller total volume. However, many dielectrics have higher breakdown field strengths than vacuum: 60-170 MV/m for teflon, 470-670 MV/m for fused silica and 2000 MV/m for diamond, compared with 20-40 MV/m for vacuum. There are several different designs in vacuum variables. The most common form is inter-meshed concentric cylinders, which are contained within a glass or ceramic vacuum envelope, similar to an electron tube. A metal bellows is used to maintain a vacuum seal while allowing positional control for the moving parts of the capacitor.

Invention Jo Emmett Jennings created the first practical vacuum variable capacitor after he founded his Jennings Radio Manufacturing Company in 1940. Commercial products have been available since 1942.

Applications Vacuum variable capacitors are commonly used in high-voltage applications: 5000 volts (5 kV) and above. They are used in equipment such as high-powered broadcast transmitters, amateur radio RF amplifiers and large antenna tuners. Industrially they are used in plasma generating equipment, for dielectric heating, and in semiconductor manufacturing. The main applications today are RF plasmas of 2 to 160 MHz where the vacuum capacitor is used as the impedance variation part in an automatic matching network in the fabrication of chips and flat panel displays.

Other variations of vacuum capacitors include fixed-value capacitors, which are designed very much like the variable versions with the exception that the adjustment mechanism is omitted.

Comparison When compared to other variable capacitors, vacuum variables tend to be more precise and more stable. This is due to the vacuum itself. Because of the sealed chamber, the dielectric constant remains the same over a wider range of operating conditions. With air variable capacitors, the air moving around the plates may change the value slightly; often it is not much but in some applications it is enough to cause undesirable effects. Vacuum variable capacitors are generally more expensive than air variable capacitors. This is primarily due to their design and the materials used. Although most use copper and glass, some may use other materials such as ceramics and metals such as gold and silver. Vacuum variables also vary in adjustment mechanisms.

References

External links

"Jennings high voltage vacuum capacitors" (PDF). amsTECHNOLOGIES. Retrieved 2021-03-18. "Technical documents of Kunshan Guoli Vacuum Electric Co., Ltd.(GLVAC) according to Vacuum Capacitors". Retrieved 2021-03-18. "Technical documents of Max-Gain Systems Inc including Jennings, Comet, Dolinko and Wilkens, General Electric, English Electric Valve according to Vacuum Capacitors". Retrieved 2023-04-13. Webarchive: Meidensha products MEIDEN AMERICA: Product overview vacuum capacitors Introduction to capacitors

Illustrations

Worked examples

Example 1 — a first encounter with Vacuum variable capacitor

Start with the simplest possible case. Write down what Vacuum variable capacitor claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Vacuum variable capacitor before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Vacuum variable capacitor ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Vacuum variable capacitor

In research: Vacuum variable capacitor appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Vacuum variable capacitor in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Vacuum variable capacitor is common in secondary-school and first-year university syllabi. It links to neighbouring topics Capacitors, Inventions by Nikola Tesla, so understanding it makes those chapters shorter.
In everyday life: Look for Vacuum variable capacitor outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Vacuum variable capacitor in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Vacuum variable capacitor means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Vacuum variable capacitor out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Vacuum variable capacitor in simple terms?

Why does Vacuum variable capacitor matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Vacuum variable capacitor?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Vacuum variable capacitor.