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#64301 - 04/05/06 02:58 PM What is the equivalent DC current...?
Cinner Offline
Member

Registered: 12/01/04
Posts: 77
Loc: 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 03:06 PM Re: What is the equivalent DC current...?
NJwirenut Offline
Member

Registered: 09/15/01
Posts: 816
Loc: Bergen County, NJ
C--1 ampere

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#64303 - 04/05/06 03:26 PM Re: What is the equivalent DC current...?
Roger Offline
Member

Registered: 05/18/02
Posts: 1779
Loc: N.C.
Actually it is (b).707

Roger

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#64304 - 04/05/06 04:04 PM Re: What is the equivalent DC current...?
JoeTestingEngr Offline
Member

Registered: 11/04/05
Posts: 786
Loc: Chicago, Il.
I agree with NJ. If you multiply the RMS by .707 again, it becomes PMS, which should be avoided.
Joe

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#64305 - 04/05/06 04:21 PM Re: What is the equivalent DC current...?
Roger Offline
Member

Registered: 05/18/02
Posts: 1779
Loc: N.C.
Oooooops, I read the question again

I also agree with NJ

Roger

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#64306 - 04/05/06 04:25 PM Re: What is the equivalent DC current...?
Cinner Offline
Member

Registered: 12/01/04
Posts: 77
Loc: Kelowna, B.C., Canada
Shouldn't the answer be:

1/0.707 = 1.41

1.41 x .637 = 0.9 amps.

Do you agree?

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#64307 - 04/05/06 04:38 PM Re: What is the equivalent DC current...?
Roger Offline
Member

Registered: 05/18/02
Posts: 1779
Loc: 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

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#64308 - 04/05/06 05:30 PM Re: What is the equivalent DC current...?
JoeTestingEngr Offline
Member

Registered: 11/04/05
Posts: 786
Loc: 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).]

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#64309 - 04/06/06 06:13 AM Re: What is the equivalent DC current...?
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: 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).

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#64310 - 04/06/06 12:28 PM Re: What is the equivalent DC current...?
RODALCO Offline
Member

Registered: 12/08/05
Posts: 863
Loc: Titirangi, Akld, New Zealand
Answer C, 1 Amp.
_________________________
The product of rotation, excitation and flux produces electricty.

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