Polar coordinates of complex impedance

[joema]

The question is: "In polar coordinates, what is the impedance of a circuit that has an admittance of 7.09 millisiemens at 45 degrees?"

The official answer is: "141 ohms at an angle of -45 degrees".

I don't understand this. 7.09 millisiemens is 141 ohms, and the positive phase angle indicates inductance, IOW a positive y value.

It seems the correct answer should be 141 ohms at an angle of 45 degrees, not -45 degrees.

Please help me understand this.

 

[tiny-tim]

hi joema!

admittance and https://www.physicsforums.com/library.php?do=view_item&itemid=303" are both complex numbers

admittance is defined as the inverse of impedance

the inverse of Re^iφ is (1/R)e^-iφ ​

(so the phase of admittance is always minus the phase of impedance)