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Capacitors
15 questions By Tony R. Kuphaldt
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Question 13 of 15
Find one or two real capacitors and bring them with you to class for discussion. Identify as much information as you can about your capacitors prior to discussion:
- Capacitance (ideal)
- Capacitance (actual)
- Voltage rating
- Type (mica, mylar, electrolytic, etc.)
Reveal answerIf possible, find a manufacturer’s datasheet for your components (or at least a datasheet for a similar component) to discuss with your classmates.
Be prepared to prove the actual capacitance of your capacitors in class, by using a multimeter (assuming your multimeter is capable of measuring capacitance)!
Notes:The purpose of this question is to get students to kinesthetically interact with the subject matter. It may seem silly to have students engage in a “show and tell” exercise, but I have found that activities such as this greatly help some students. For those learners who are kinesthetic in nature, it is a great help to actually touch real components while they’re learning about their function. Of course, this question also provides an excellent opportunity for them to practice interpreting component markings, use a multimeter, access datasheets, etc.
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Question 14 of 15
An important parameter in capacitor performance is ESR. Define ESR, and explain what causes it.
Reveal answer“ESR” stands for Equivalent Series Resistance, usually being a consequence of the capacitor’s dielectric substance.
Notes:Discuss with your students why ESR matters, especially in decoupling applications where capacitors are expected to handle large [dv/dt] transients.
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Question 15 of 15
Capacitors often have letter codes following the three-digit number codes. For example, here are some typical capacitor codes, complete with letters:
- 473K
- 102J
- 224M
- 331F
Determine the meaning of letters used on capacitor labels, what the respective numeric values are for all the available letters, and then finally what these four specific number/letter codes mean (shown above).
Reveal answerLetter codes are used to designate tolerance, just like the last color band on most resistors. I will let you research the letter code equivalencies on your own! Same for the specific values of the four capacitor labels shown.
Notes:The capacitor tolerance codes are easy enough for students to research on their own. For your own reference, though:
- D = ± 0.5%
- F = ± 1%
- G = ± 2%
- H = ± 3%
- J = ± 5%
- K = ± 10%
- M = ± 20%
- P = 100%, -0%
- Z = 80%, -20%
Same for the four capacitor labels given in the question:
- 473K = 47 nF ± 10%
- 102J = 1 nF ± 5%
- 224M = 0.22 μF ± 20%
- 331F = 330 pF ± 1%
