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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?

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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?

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  • \$\begingroup\$ 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 \$\endgroup\$ – Sunnyskyguy EE75 Sep 8 '18 at 0:25
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In 4.2b, you have +10V at the top of the circuit, so the cathode must be more positive than the anode. In that case, the diode acts as an open circuit - no current will flow, so there is no voltage drop across the resistor, and 10 volts, with polarity as shown, across the diode.

The + and - signs beside the diode indicate the polarity of the voltage applied to the diode.

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  • \$\begingroup\$ why is anode called the positive terminal then? clearly, in that figure, the anode is at a lower potential right? Also, in fig 4.1b, in the graph, what does -v indicate if the voltage drop across the diode is +v? \$\endgroup\$ – David Sep 7 '18 at 23:05
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    \$\begingroup\$ "Anode" and "Cathode" are the names of the terminals of the diode - they don't change just because you turn the diode around, or the circuit applies a voltage the "wrong" way. You don't call the front of your car "the back" when you are backing up, do you? \$\endgroup\$ – Peter Bennett Sep 7 '18 at 23:11

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