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Joined: Dec 2004
Posts: 78
C
Cinner Offline OP
Member
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).]

Joined: Sep 2001
Posts: 806
N
Member
C--1 ampere

Joined: May 2002
Posts: 1,716
R
Member
Actually it is (b).707

Roger

Joined: Nov 2005
Posts: 827
Likes: 1
J
Member
I agree with NJ. If you multiply the RMS by .707 again, it becomes PMS, which should be avoided.
Joe

Joined: May 2002
Posts: 1,716
R
Member
Oooooops, I read the question again [Linked Image]

I also agree with NJ

Roger

Joined: Dec 2004
Posts: 78
C
Cinner Offline OP
Member
Shouldn't the answer be:

1/0.707 = 1.41

1.41 x .637 = 0.9 amps.

Do you agree?

Joined: May 2002
Posts: 1,716
R
Member
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

Joined: Nov 2005
Posts: 827
Likes: 1
J
Member
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).]

Joined: Aug 2001
Posts: 7,520
P
Member
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).

Joined: Dec 2005
Posts: 869
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R
Member
Answer C, 1 Amp.


The product of rotation, excitation and flux produces electricty.
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