Electromagnetism - RLC Circuit


An AC circuit consists of the elements shown above, with R = 10,000 ohms, L = 25 millihenrie and C an adjustable capacitance. The AC voltage generator supplies a signal with amplitude of 40 volts and angular frequency of 1,000 radians per second. For what value of C is the amplitude of the current maximized?

A. 4 nF
B. 40 nF
C. 4 μF
D. 40 μF
E. 400 μF
(GR0177 #38)
Solution:

Imax when XL = XC

→ ωL = 1 / ωC

1 / ω2L 
= 1 / [(103)× 25 × 10−3]
= 1 / (25 × 103)
= 40 × 10−6 
= 40 μF

Answer: D

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