#9, 10 soultion plz! thanks 9) what is maximum energy stored in capacitor? -- an

Question

#9, 10 soultion plz! thanks

9) what is maximum energy stored in capacitor? -- answer is B

10) suppose generator frequency is now increased to a very large value. In this case,the generator voltage will -- answer is C

Physics 212A Spring 2012 Exam III The next three questions pertain to the situation described below. In the RLC circuit shown at right, the generator voltage can be represented by at Enex sin(ar). The capacitance C HF, the resistance R 160 s, the inductance L 170 mH, the peak generator voltage Enax 12 V and the angular frequency a 900 rads. we hao to assume 8. What is Imax the peak value of the current oscillations in the circuit? Em 75 mA c) 93 mA d) 123 mA e) 157 mA 9. Suppose the maximum generator voltage is changed such that the maximum current is l ther circuit component values remain the What is the maximum same energy stored in the capacitor? Em Trn 22- I ut a) 1.4 mJ b) 20 m c) 54 mJ 10. Suppose the generator frequency is now increased to a very large value. In this case the generator voltage a) lag the current by nearly 900 the current b) have nearly the same phase as c) lead the current by nearly 90°

Explanation / Answer

9. Peak current in the circuit is I = 0.8A

reactance of the capacitor Xc = 55.56

So peak voltage Vc across the capacitor is Vc = IXc = (0.8A)(55.56) = 44.448V

So maximum energy stored in the capacitor is E = (1/2)CVc2

or E = (0.5)(20X10-6F)( 44.448V)2

or E = 19.756mJ

So b) 20mJ is the correct option.

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10. the reactance of capacitance is given by Xc = 1/(C), so if becomes very large,  Xc would tend towards zero. And XL = L would become very large.

Now reactance of the ciruit will be X = Xc - XL will be negative as XL > XC

So, the pahse is given by tan = (Xc - XL)/R, so pahse will also be negative as Xc - XL is negative.

also since XL has become very large

tan = (Xc - XL)/R would tend to -, and so = -900, nearly

Which makes the current lag behind the voltage by nearly 900, or equivalently voltage leads the current by nearly 900.

So, the correct option is c)

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This concludes the answers. Check the answer and let me know if it's correct. If you need any more clarification or correction, feel free to ask.....

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