Hello, there's a question that I've been wondering for ages. Why is impedance considered when connecting circuits/devices? (I know that impedance is the square root of [R^2 + Xl^2 - Xc^2], so don't worry about that).

I've read that input impedance should be lower than the output impedance of the circuit connected, why is this? The way I see it, a high output impedance will lower the current, which reduces signal strength; which leads to inefficiency.

Also, how are manufacturers able to define impedance? Take an 8R speaker, for example. The impedance will obviously change when an alternating signal is applied to it!

I've read that input impedance should be lower than the output impedance of the circuit connected, why is this? The way I see it, a high output impedance will lower the current, which reduces signal strength; which leads to inefficiency.

Also, how are manufacturers able to define impedance? Take an 8R speaker, for example. The impedance will obviously change when an alternating signal is applied to it!

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