What is the rms current draw of a microwave operating at 1180 W and 120 Vrms?

[saritche]

Homework Statement

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

Homework Equations

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

The Attempt at a Solution

I=P/V
Peak=I^2R
Vrms=.707V

 

[lanedance]

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]

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

 

[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]

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]

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!