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Find current at high/low frequency 
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#1
Oct310, 12:54 AM

P: 61

1. The problem statement, all variables and given/known data
find the rms current delievered by the 45v (rms) power supply when a) the frequency is very large and b) the frequency is very small. answer: a) 225mA, b) 450mA http://yfrog.com/jucurrentqg Uploaded with ImageShack.us 2. Relevant equations w= angular velocity (supposed to be omega) L= inductor C= capacitor j= complex coefficent = sqrt(1) Zl= resistance of inductor Zc= resistance of capacitor Ztot= total resistance R= resistance of resistor P= Power Xl=wL Xc=1/wc Zl=j*Xl Zc=j*Xc Ztot= R + Zl + Zc = R + j(XlXc) 3. The attempt at a solution with frequency just being high, how am I supposed to get these exact numbers without letters/symbol for I? o.o I tried the calculation and omega did not cancel out either. 


#2
Oct310, 02:24 AM

P: 1,261

The key idea is that in the case of very high or very low frequency, you can take the impedance (resistance) of the inductor and capacitor to be ~infinite, respectively. Does it make sense why that's true (as an approximation at least)?
In effect, this eliminates one of the two loops in the circuit for each case. 


#3
Oct410, 02:19 PM

P: 61

thank you 


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