Problem 91-7    Source:  Adaptade example 10.6 - page 430 - SUDHAKAR, A. & PALLI, Shyammohan -    Book: Electrical Circuits Analysis - 1ª edition - Ed. McGrawHill - 2009.

An amplifier with an output impedance of 1,936 Ω must drive a speaker with an impedance of 4 Ω.

a) Calculate the transformation ratio of the transformer to interconnect the two systems.

b) A current of 20 mA and 500 Hz flows in the primary. Calculate the current in the secondary of the transformer at a frequency of 500 Hz.

c) What is the power supplied to the speaker?

Solution of the Problem 91-7

Item a

We know that for maximum power transfer to the speaker, the impedances must satisfy the relationship below:

Substituting the numerical values, we find:

So the transformation ratio is:

Item b

We know that:

Substituting the numerical values, we find:

Item c

The power supplied to the load is: