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What is the resistance value?
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huji



Joined: 15 Jul 2004
Posts: 79
Helped: 1
Post01 Jul 2005 10:37   

What is the resistance value?
Hi,
If a capacitor (1uF) is parallel with resistor (1kΩ) and an ac supply ( 2Vp with
1 kHz) were connected to it. what would the resistance be??

Is it 1 kΩ due to capacitor short circuit in ac condition or 0Ω?
And if a 10 Vdc supply where to replace the ac supply would the resistance be 1kΩ due to open circuit in capacitor?

And what about a inductor (1mH )parallel with resistor (1kΩ) what would the value of resistance be from ac and dc side of view..

Thanks
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DrWhoF



Joined: 06 May 2005
Posts: 334
Helped: 12
Post01 Jul 2005 11:01   

Re: What is the resistance value?
In mixed circuits you should rather use impedance.
At 1kHz 1µF capacitance will have ≈160Ω so together with 1kΩ resictor in parallel it will be ≈138Ω.
At 0Hz (dc) you will only read resistance.

With inductance the story is different. The lowest impedance you will have at dc (in theory 0Ω, in practice this will be resistance of wire used to construct this inductor.
The higher the frequency the higher the impedance of an iductor, and you can use the basif formula to calculate its value: Z(L)=2*Π*f*L or just ωL.

DrWhoF
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MRFGUY



Joined: 16 Sep 2003
Posts: 109
Helped: 5
Post01 Jul 2005 11:02   

Re: What is the resistance value?
huji wrote:
Hi,
If a capacitor (1uF) is parallel with resistor (1kΩ) and an ac supply ( 2Vp with
1 kHz) were connected to it. what would the resistance be??

Is it 1 kΩ due to capacitor short circuit in ac condition or 0Ω?


Concern with ac we have to say impedence. It include both resistance and reactance. Equations will be like this:

Z=R || 1/(j2pi f C);

huji wrote:
And if a 10 Vdc supply where to replace the ac supply would the resistance be 1kΩ due to open circuit in capacitor?


For dc we only have resistance. so 10kΩ.

huji wrote:

And what about a inductor (1mH )parallel with resistor (1kΩ) what would the value of resistance be from ac and dc side of view.


For AC Z=R || (j2 pi fL);
For dc we can assume inductor as short circuits. So 0Ω.



Thanks
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