Answer to Question 9

A loudspeaker has an inductance of 1.25 × 10^{4} H
and a resistance of 4.0
W.
It is connected in series with an inductor of inductance 3.0
× 10^{5} H and resistance 1.0
W.
A frequency of 1400 Hz is passed through the loudspeaker.
Calculate: 
Model the speaker and the low pass filter as two inductors in series and two resistors in series. (a) Speaker: X_{L} = 2p × 1400 Hz × 1.25 × 10^{4} Hz = 1.10 W Inductor: X_{L} = 2p × 1400 Hz × 3.0 × 10^{5} Hz = 0.264 W
(b) Total inductance = 1.10 W + 0.264 W = 1.36 W Total resistance = 4.0 W + 1.0 W = 5.0 W Impedance: Z^{2} = (5.0 W)^{2} + (1.36 W)^{2} = 26.86 W^{2} Z = 5.2 W (2 s.f.)
