# Inductors vs. Capacitors

Discussion in 'General Electronics Chat' started by hondabones, Feb 5, 2010.

1. ### hondabones Thread Starter Active Member

Sep 29, 2009
123
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Hello All!

I noticed a few similarities in the calculations. Like, inductors in series are calculated similar to resistors in series. However, caps in series are similar to resistors in parallel.

If you compare the two components (caps and inductors) they are basically inverses of each other. I am having trouble understanding the practical application and the purpose of these two components.

They have such a unique relationship there must be some reasoning behind this. We are already beginning to learn series RLC circuits. I would like to understand the inductor vs. the capacitor before we combine the two components.

Jim

2. ### MikeML AAC Fanatic!

Oct 2, 2009
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The light bulb will go off when you study "resonant circuits".

3. ### hondabones Thread Starter Active Member

Sep 29, 2009
123
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We did study resonate frequency just yesterday. There is no light bulb involve at this time so I don't understand your post at this time.

Thank you for your reply. I welcome any input. I absolutely love my decision to get into electronics.

4. ### MikeML AAC Fanatic!

Oct 2, 2009
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The nugget that you obviously missed while studying resonant circuits is that capacitive reactance cancels inductive reactance.

5. ### hondabones Thread Starter Active Member

Sep 29, 2009
123
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Your probably right. I know that when XL goes up XC goes down. Let me rephrase that. As frequency goes down XL goes up and XC goes down. At the point where XL and XC are the same is resonate frequency. Did I accurately state this?

6. ### alphacat Active Member

Jun 6, 2009
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As frequency decreases, XL (ωL) decreases and XC (1/[ωC]) increases.

7. ### KL7AJ AAC Fanatic!

Nov 4, 2008
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Here's a little algebraic gymnastics you can do, if you're up to it. In fact, I just demonstrated it to my class last night!

XL = 2*pi*fL
XC = 1/2*fC

Set 2*pi*fL= 1/2*pi*fC

Now solve for f.

This will give you the resonant frequency formula in terms of L and C.

Great exercise.

eric

8. ### hondabones Thread Starter Active Member

Sep 29, 2009
123
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No kidding! We just learned that last night in class too.

f = 1/2pi√(LC)

9. ### russ_hensel Distinguished Member

Jan 11, 2009
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Both inductors and caps. shift the phase relationship between voltage and current. In exactly opposite directions. Becomes much clearer in the complex plane. Wait for it, it is so cool.

10. ### Von Active Member

Oct 29, 2008
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ELI the ICE-man!

11. ### AllVol AAC Fanatic!

Nov 22, 2005
55
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Real numbers and imaginary ones!

12. ### hondabones Thread Starter Active Member

Sep 29, 2009
123
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ELI the ICE person

As my instructor puts it

13. ### Ron H AAC Fanatic!

Apr 14, 2005
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That's still sexist. "Son" is gender-specific. it should be ELI the ICE perchild.

Sep 29, 2009
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Good point.

15. ### jans123 New Member

Jan 30, 2010
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Another aspect is that inductors and capicators store energy, resistors don't. Inductors can give the energy away as very nasty high voltage when circuits opens and capacitors can deliver banging currents when circuits closes.
Resistors just tries to convert the energy it gets into heat.

OUCH!

16. ### hondabones Thread Starter Active Member

Sep 29, 2009
123
1

You're saying that inductors effect voltage and caps effect current. Right?

17. ### jans123 New Member

Jan 30, 2010
20
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In a way... yes, but it is more complex than that. Inductors don't like changes in current and tries to keep it constant. It has to do with the magnetic fields building up and braking down. It stores energy as a magnetic fild, whilst capicators shuffles charges (electrons) and don't like changes in the voltage.
It is really the moving electrons in the inductor that creates the magnetic field and if you tries to break the current trough a inductor the collapsing magnetic field will induce voltage in the windings that tries to keep the electrons going at the same rate, whatever the sice of the beak in the circuit are, that's why a arch of current (sorry my English vocabulary is limited) flow between the contacts and damage the switches. On the other hand, the capicator stores energy as electrons and the bigger the difference is between the voltage on the capicator and the voltage source is when you connect it, the bigger the current are when the switch is turned on.

Sorry, can't give a simple answer. If I try i would probably end up in an even bigger confusion.

18. ### KL7AJ AAC Fanatic!

Nov 4, 2008
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He he! Well, obviously great minds travel the same rails.

eric