Resistors in series/parallel
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Resistors in series/parallel

 
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Joachim
Guest
Posted: Mon Nov 14, 2005 5:35 pm    Post subject: Resistors in series/parallel Reply with quote
What will be the combined resistance of this combination of resistors:

http://krebs.uk.com/joachim/resistor.jpg

Thanks in advance,

Joachim

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Tim Williams
Guest
Posted: Mon Nov 14, 2005 5:35 pm    Post subject: Re: Resistors in series/parallel Reply with quote
"Joachim" <jkrebs@gmail.com> wrote in message
news:1131986646.978771.320380@g14g2000cwa.googlegroups.com...
Quote:
What will be the combined resistance of this combination of resistors:

http://krebs.uk.com/joachim/resistor.jpg

42.

Tim

--
Deep Fryer: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
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John - kd5yi
Guest
Posted: Mon Nov 14, 2005 11:49 pm    Post subject: Re: Resistors in series/parallel Reply with quote
"Joachim" <jkrebs@gmail.com> wrote in message
news:1131986646.978771.320380@g14g2000cwa.googlegroups.com...
Quote:
What will be the combined resistance of this combination of resistors:

http://krebs.uk.com/joachim/resistor.jpg

Thanks in advance,

Joachim


(R1 || R2) + (R3 || R4).

Or not.

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Noway2
Guest
Posted: Tue Nov 15, 2005 12:01 am    Post subject: Re: Resistors in series/parallel Reply with quote
This is a classic problem for circuit analysis classis as the diamond
shape configuration throws alot of people off. In order to determine an
equivalent value, it is necessary to pick the problem apart in smaller
step.

First, redraw the circuit in a more familiar form with the resistors
drawn horizontally and vertically.

Once that is done, you should be able to see that the circuit is a
simple series - parallel combination. Proceed through the circuit,
simplifying the parallel combinations to get the single value
equivalence.
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Joachim
Guest
Posted: Tue Nov 15, 2005 1:35 am    Post subject: Re: Resistors in series/parallel Reply with quote
Thanks for your help, I would be happy if you could now help me confirm
this:

R1 = 1/2
R2 = 3/2
R3 = 1/2
R4 = 3/2
R5 = 1/2

Does Rtot = 3/4 ?
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Fester
Guest
Posted: Tue Nov 15, 2005 1:35 am    Post subject: Re: Resistors in series/parallel Reply with quote
Joachim wrote:

Quote:
What will be the combined resistance of this combination of resistors:

http://krebs.uk.com/joachim/resistor.jpg

Thanks in advance,

Joachim

Please,

Do your own homework... We already graduated but on our own.

Fester
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petrus bitbyter
Guest
Posted: Tue Nov 15, 2005 1:35 am    Post subject: Re: Resistors in series/parallel Reply with quote
"Joachim" <jkrebs@gmail.com> schreef in bericht
news:1131986646.978771.320380@g14g2000cwa.googlegroups.com...
Quote:
What will be the combined resistance of this combination of resistors:

http://krebs.uk.com/joachim/resistor.jpg

Thanks in advance,

Joachim


Joachim,

That's hard to say without knowing the values of the resistors involved.
Besides, aren't you supposed to find the solution yourself?

petrus bitbyter
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Bob Monsen
Guest
Posted: Tue Nov 15, 2005 1:35 am    Post subject: Re: Resistors in series/parallel Reply with quote
On Mon, 14 Nov 2005 08:44:07 -0800, Joachim wrote:

Quote:
What will be the combined resistance of this combination of resistors:

http://krebs.uk.com/joachim/resistor.jpg

Thanks in advance,

Joachim

Use the PI -> WYE conversion formula for R1,R2,and R5. That simplifies
it...

ra=r1*r2/(r1+r2+r3)
rb=r1*r5/(r1+r2+r3)
rc=r2*r5/(r1+r2+r3)

Then, r = ra + parallel(rb+r3,rc+r4)

so

r = (r1 r2 r3 + r1 r2 r4 + r1 r2 r5 + r1 r3 r4 + r2 r3 r4 + r1 r4 r5 +

r2 r3 r5 + r3 r4 r5) / (r1 r3 + r1 r4 + r2 r3 + r1 r5 + r2 r4 + r2 r5 +

r3 r5 + r4 r5)

---
Regards,
Bob Monsen

One cannot inquire into the foundations and nature of mathematics without
delving into the question of the operations by which the mathematical
activity of the mind is conducted. If one failed to take that into account,
then one would be left studying only the language in which mathematics is
represented rather than the essence of mathematics.
- Luitzen Brouwer
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John - KD5YI
Guest
Posted: Tue Nov 15, 2005 9:35 am    Post subject: Re: Resistors in series/parallel Reply with quote
Joachim wrote:
Quote:
Thanks for your help, I would be happy if you could now help me confirm
this:

R1 = 1/2
R2 = 3/2
R3 = 1/2
R4 = 3/2
R5 = 1/2

Does Rtot = 3/4 ?


Yes.
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PeteS
Guest
Posted: Tue Nov 15, 2005 5:35 pm    Post subject: Re: Resistors in series/parallel Reply with quote
This is a classic Wheastone bridge.

Look it up (Wikipedia has a good article :
http://en.wikipedia.org/wiki/Wheatstone_bridge) and learn about it.

Cheers

PeteS
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Bob Monsen
Guest
Posted: Wed Nov 16, 2005 1:35 am    Post subject: Re: Resistors in series/parallel Reply with quote
On Tue, 15 Nov 2005 04:58:14 +0000, John - KD5YI wrote:

Quote:
Joachim wrote:
Thanks for your help, I would be happy if you could now help me confirm
this:

R1 = 1/2
R2 = 3/2
R3 = 1/2
R4 = 3/2
R5 = 1/2

Does Rtot = 3/4 ?


Yes.

Cute. Now, try R1/R3 != R2/R4.

The OPs homework was probably presented with these values, and he tried to
derive an equation for the resistance, without realizing that R5 doesn't
pass any current... The problem is a bit harder if you don't notice that
fact.

---
Regards,
Bob Monsen

Ah, Why, ye Gods, should two and two make four? - Alexander Pope
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