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#64301 - 04/05/06 05:58 PM What is the equivalent DC current...?  
Cinner  Offline
Member
Joined: Dec 2004
Posts: 78
Kelowna, B.C., Canada
What is the DC current value that will give you the same amount of heat as 1.0 amp rms going through a 10 ohm resistor?

A).637 a
b) .707 a
c) 1.0 a
d) 1.41 a



[This message has been edited by Cinner (edited 04-05-2006).]


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#64302 - 04/05/06 06:06 PM Re: What is the equivalent DC current...?  
NJwirenut  Offline
Member
Joined: Sep 2001
Posts: 806
Bergen County, NJ
C--1 ampere


#64303 - 04/05/06 06:26 PM Re: What is the equivalent DC current...?  
Roger  Offline
Member
Joined: May 2002
Posts: 1,716
N.C.
Actually it is (b).707

Roger


#64304 - 04/05/06 07:04 PM Re: What is the equivalent DC current...?  
JoeTestingEngr  Offline
Member
Joined: Nov 2005
Posts: 782
Chicago, Il.
I agree with NJ. If you multiply the RMS by .707 again, it becomes PMS, which should be avoided.
Joe


#64305 - 04/05/06 07:21 PM Re: What is the equivalent DC current...?  
Roger  Offline
Member
Joined: May 2002
Posts: 1,716
N.C.
Oooooops, I read the question again [Linked Image]

I also agree with NJ

Roger


#64306 - 04/05/06 07:25 PM Re: What is the equivalent DC current...?  
Cinner  Offline
Member
Joined: Dec 2004
Posts: 78
Kelowna, B.C., Canada
Shouldn't the answer be:

1/0.707 = 1.41

1.41 x .637 = 0.9 amps.

Do you agree?


#64307 - 04/05/06 07:38 PM Re: What is the equivalent DC current...?  
Roger  Offline
Member
Joined: May 2002
Posts: 1,716
N.C.
Cinner, the "rms" (which I somehow read as "AC" when I first read the question, who knows where my reading skills jaunted off to) already has the AC value equal to the DC value.

Roger


#64308 - 04/05/06 08:30 PM Re: What is the equivalent DC current...?  
JoeTestingEngr  Offline
Member
Joined: Nov 2005
Posts: 782
Chicago, Il.
Cinner,
A few years ago, meters started coming out with the "True RMS" labels all over them. These meters give you a reading that is already the peak value X .707, or the RMS, or the heating value. If you had a less spiffy, average reading meter, you would take the displayed "average" value / .637, to get to peak, and then X .707 to get to your RMS value. Hope this helps.
Joe
But still avoid the PMS.

[This message has been edited by JoeTestingEngr (edited 04-05-2006).]


#64309 - 04/06/06 09:13 AM Re: What is the equivalent DC current...?  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
And the 10-ohm figure specified is one of these pieces of data thrown in to a question which is of no significance.

Since P = I^2 x R, 1 amp DC will give the same amount of heat as 1 amp RMS AC no matter what the resistance value (so long as it's the same in both cases, of course).


#64310 - 04/06/06 03:28 PM Re: What is the equivalent DC current...?  
RODALCO  Offline
Member
Joined: Dec 2005
Posts: 854
Titirangi, Akld, New Zealand
Answer C, 1 Amp.


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