I truly wish I understood what you're all talking about. I get resistance, but impedance goes right by me. How can it impede but not resist? Not being smart...
Think in terms of the opposition to the flow of electricity to keep the terms clear.
Plain resistance and impedance are both a forms of opposition to the flow of electricity.
In simple terms pure resistance (just a resistor) in a circuit behaves the same whether the signal is AC (alternating current) or DC (direct current).
If we also include an inductor, a capacitor or both, then the circuit will behave differently on AC and DC and how it behaves is frequency dependent.
The opposition to the flow of AC electricity when an inductor and/or a capacitor are also included is called impedance. It will vary with frequency.
The contribution to the opposition to the flow of AC electricity by a capacitor is called capacitive reactance and the opposition to the flow of AC electricity contributed by an inductor is called inductive reactance. These values will vary with frequency.
Impedance is made up of the resistance that is in a circuit plus the capacitive reactance (from a capacitor) or inductive reactance (from an inductor) or both.
Impedance in an AC circuit is the sum of the opposition to the flow of electricity from pure resistance in the circuit plus any opposition supplied by a capacitor, inductor or both.
To be clear all circuits will contain at least some resistance, capacitance and inductance, so there will always be a difference in the way the circuit behaves with DC and AC electricity, all though depending on the circuit these differences may be quite small.
It is common practice to refer to the opposition to the flow of electricity in a DC circuit as resistance and the opposition to the flow of electricity in an AC circuit as impedance, even with out knowing the actual make up of the circuit in terms of resistance, capacitance and or inductance.
Phono cartridges, whether moving magnet, moving iron or moving coil all contain an electrical generator made up of a magnet and coils of wire. The coils of wire are inductors and since the audio signal generated by the phono cartridge is AC (alternating current) electricity we speak of a phono cartridge as having specific impedance. This impedance will vary with frequency.
We also speak of the DC resistance of the wire of the coils in the phono cartridge. This does not vary with frequency.
We also speak of the input of the phono preamplifier in terms of its impedance (how it behaves with AC electricity (the signal from the phono cartridge). This will vary with frequency.
We also speak of the purely resistive component of the impedance of the phono preamplifier because phono cartridge manufactures may specify a certain range of DC resistance loading for their phono cartridge. This does not vary with frequency. This is what we vary when adding resistors in parallel (parallel loading) with the input of the phono preamplifier.
We also speak of the capacitance of the input of the phono preamplifier because cartridge manufacturers may specify a range of capacitive loading for their phono cartridge. The contribution to the opposition to the flow of the electricity generated by the phono cartridge will vary with frequency.
To end in
simple terms, we speak of the opposition to the flow of electricity in a DC circuit as resistance and the opposition to the flow of electricity in an AC circuit as impedance. The impedance is the sum of the opposition to the flow of AC electricity provided by the plain resistance in the circuit plus the contribution to the opposition to the flow of the AC electricity provided by any capacitance and or inductance. The contribution to the opposition to the flow of AC electricity provided by the capacitance and inductance will vary with frequency.
Resistance can be measured with a DMM but measuring impedance is more complicated.
Impedance and resistance are sometimes (although not correctly) used interchangeably.
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