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What is the equivalent DC current...? #64301
04/05/06 04:58 PM
04/05/06 04:58 PM
C
Cinner  Offline OP
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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Re: What is the equivalent DC current...? #64302
04/05/06 05:06 PM
04/05/06 05:06 PM
N
NJwirenut  Offline
Member
Joined: Sep 2001
Posts: 806
Bergen County, NJ
C--1 ampere

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

Roger

Re: What is the equivalent DC current...? #64304
04/05/06 06:04 PM
04/05/06 06:04 PM
J
JoeTestingEngr  Offline
Member
Joined: Nov 2005
Posts: 791
Chicago, Il.
I agree with NJ. If you multiply the RMS by .707 again, it becomes PMS, which should be avoided.
Joe

Re: What is the equivalent DC current...? #64305
04/05/06 06:21 PM
04/05/06 06:21 PM
R
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

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

Re: What is the equivalent DC current...? #64307
04/05/06 06:38 PM
04/05/06 06:38 PM
R
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

Re: What is the equivalent DC current...? #64308
04/05/06 07:30 PM
04/05/06 07:30 PM
J
JoeTestingEngr  Offline
Member
Joined: Nov 2005
Posts: 791
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).]

Re: What is the equivalent DC current...? #64309
04/06/06 08:13 AM
04/06/06 08:13 AM
P
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).

Re: What is the equivalent DC current...? #64310
04/06/06 02:28 PM
04/06/06 02:28 PM
R
RODALCO  Offline
Member
Joined: Dec 2005
Posts: 856
Titirangi, Akld, New Zealand
Answer C, 1 Amp.


The product of rotation, excitation and flux produces electricty.
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