# Finding delay angle ,Vrms, Irms using AC voltage/ load resistor

1. Apr 28, 2013

### pokie_panda

1. The problem statement, all variables and given/known data

From the average power consumed by the lamp in a light dimmer circuit connected to 240V AC main,
What is the expression for RMS voltage,
calculate the range of values of the delay angle α,(i)RMS voltage (ii)RMS current in the lamp, (iii) the average power if its nominal ratings are 240 V AC, 40 W.

2. Relevant equations

P=Vrms^2/2∏R (∏-α+1/2sin(2α))
R= load resistance
Vrms= amplitude of supply voltage
α=delay

3. The attempt at a solution
This is where i'm not sure ,
if we have the nominal ratings of 240V AC and 40 W,
we know that
Vrms = 240/sqrt(2)
=169.7
Then from the equation above solve for α

Last edited: Apr 28, 2013
2. Apr 28, 2013

### pokie_panda

Don't worry i figured it out

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