Resistance: In a device, component, or circuit, the simple opposition to current flow. Resistance by itself causes nophase shift. In a purely resistive circuit, R= E/I, where R is the resistance in ohms, E is the voltage in volts, and I is the current in amperes.
Impedance: The total opposition offered by a circuit or device to the flow of alternating current. It is the vector sum of RESISTANCE and REACTANCE. This is a COMPLEX NUMBER whose real-number component is resistance R, and whose imaginary-number component is reactance jX; mathematically, Z= R+ jX.
Regards, svicent