Curious about the resistance of an audio speaker, Luke Klaus Lee measures the resistance of a speaker which is labeled as having a6 Ω impedance. The voltmeter’s lowest scale is 200Ω and only gives one digit. Wanting more than one digit, he meditates on this and his mantra gives him the solution to the measurement problem: Ohm’s Law! Luke gauges the voltage of a D cell battery to be 1.45 V. He connects this to the speaker and the meter, in current measuring mode, and gets a reading of 0.22A.
Suppose that the rated impedance has about one important digit (6means among 5.5 and 6.5). The frequencies of the electrical signals to the speaker are the same as the audio frequencies it produces (look in the sound chapter for this range).
a) What is the range of frequencies involved?
b) What is the range of possible values for the inductance of the speaker coil if the impedance is to be in the range 5.5 to 6.5 over the range of audio frequencies? Do these values seem reasonable for such a coil?