Current and the root mean square

[DrMattOglesby]

I dont know when to take the Irms of a current.
i know the equation is Imax/(sq.rt. of 2)
i also know its used when discussing direct or alternating currents.

i just dont get why i need to use the equation or what it means if and when i do.

can someone please explain that for me?
thanks

is it just a way of identifying the total current in an alternating current???

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[tf2medic]

is it just a way of identifying the total current in an alternating current???

yep. AC circuits are sinusoidal so if you actually tried to find the total current the same way as in DC circuits then you'll just get 0 everytime because the + and - values cancel each other out all the way through. irms is the root mean square of current. it comes from the power equation P=i^2 * r. To find the average power you have to find the average i^2 over one period, which is irms^2. So...solve for irms

irms^2=[(imax)^2)]/2
irms = imax/root2

i'm glad you asked this..made me review too

 

[tncekm]

yep. AC circuits are sinusoidal so if you actually tried to find the total current the same way as in DC circuits then you'll just get 0 everytime because the + and - values cancel each other out all the way through. irms is the root mean square of current. it comes from the power equation P=i^2 * r. To find the average power you have to find the average i^2 over one period, which is irms^2. So...solve for irms

irms^2=[(imax)^2)]/2
irms = imax/root2

i'm glad you asked this..made me review too

Well explained.

 

[DrMattOglesby]

yeah and i apologize if i ask some pretty obvious questions...its been 6 years since i was last in a physics class, and even then i only made a B and a C letter grade =/
so i just have to review everything all over again. thanks for your help guys.
ill have some more questions as time goes on.
-matt

 

[tncekm]

No such thing as a dumb question, but there are dumb people who refuse to ask questions