# Rms current in microwave

#### saritche

1. Homework Statement
peak power consumed by microwave is 1180 W when operated at 120 Vrms. What rms current does that microwave draw?

2. Homework Equations
I'm not getting the correct answer, I think I am getting I and V confused with Irms and Vrms and Imax.

3. The Attempt at a Solution
I=P/V
Peak=I^2R
Vrms=.707V
1. Homework Statement

2. Homework Equations

3. The Attempt at a Solution
1. Homework Statement

2. Homework Equations

3. The Attempt at a Solution

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#### lanedance

Homework Helper
so waht answer do you get & how?

#### saritche

I found a value for R with P=V^2/R and tried plugging that into P=I^2R, then I took that I multiplied by .707

#### lanedance

Homework Helper
best to work all in rms or all in peak, never combine the 2

note Vrms = Vp/sqrt(2) where Vp is peak V
and Irms = Ip/sqrt(2)

If P = VI, what is the relation between peak & avg power

If we say

Pavg = Vrms.Irms
Pp = Vp.Ip

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#### saritche

thats the part I don't understand, how to combine the two equations to get the relationship between the two, are they equal because power is conserved?

#### lanedance

Homework Helper
P=VI is always true & its fine to use either (rms or peak), so you know you are working in peak or rms exclusively

if you combine the definitions below they give
Pp = 2.Pavg
this is probably where the confusion comes in

so convert to avg power then use P = VI

#### saritche

the answer is just not coming out:
I plugged in Ppeak=2(Vrms*Irms)
which is 1180=2(120)*2Irms
1180/240=2Irms
Irms=2.458

am I not getting something? or is it a number thing?

#### lanedance

Homework Helper
the answer is just not coming out:
I plugged in Ppeak=2(Vrms*Irms)
which is 1180=2(120)*2Irms
? you have added an extra factor of two here, any reason?

1180/240=2Irms
Irms=2.458

am I not getting something? or is it a number thing?

#### saritche

I assumed I had to multiply 2 times each factor 2(VI). I got it now... thank you so much for your help!

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