# confused about diode polarity vs circuit polarity

I know the anode has a + sign and cathode has negative sign. But are these signs reversed depending on how the diode is connected with the circuit?

In the above pic, in fig 4.2b, why isnt the - sign on the top and + sign on the bottom of the diode, since the cathode is on the top side? Also, what does -v indicate in fig 4.2b?

• Note that Fig 4.2 (b) violates every known datasheet Absolute Maximum for Vr ( if it were an LED) Although we refer to Zeners as the reverse Voltage -V they are often assumed positive as if you understand it is an absolute value as a component – Tony Stewart Sunnyskyguy EE75 Sep 8 '18 at 0:25
• Think of the diode as a push/pull type door. From the Push side you can go right threw with no resistance(no voltage drop). From the pull side if you push it blocks you. Now with enough force(Breakdown voltage) you will eventually get through. – Robert Fay Sep 17 '19 at 20:43