Curious about the resistance of an audio speaker, Luke KlausLeemeasures the
resistance of a speaker which is labeled as having a 6Ωimpedance.The voltmeterâs
lowest scale is 200Ω and only gives one digit. Wanting morethan onedigit, he meditates
on this and his mantra gives him the solution to themeasurementproblem: Ohmâs Law!
Luke measures the voltage of a D cell battery to be 1.45 V.Heconnects this to the
speaker and the meter, in current measuring mode, and gets areadingof 0.22A.
Assume that the rated impedance has about one significant digit(6means between 5.5
and 6.5). The frequencies of the electrical signals to thespeakerare the same as the
audio frequencies it produces (look in the sound chapter forthisrange).
(a) What is the range of frequencies involved?
(b) What is the range of possible values for the inductance ofthespeaker coil if the
impedance is to be in the range 5.5 to 6.5 over the range ofaudiofrequencies? Do these
values seem reasonable for such a coil?
