Why do diede has two resistance values in ieone in forward bias other in reverse bias?

Answer 1

If you are talking about reverse biasing a diode, then you are talking about a zener diode. A zener diode, like a normal diode, has a forward bias around 0.7 volts (depending on current and temperature). Using Ohm's law, you can calculate the effective resistance of the diode in forward bias. (Example: 0.7 volts, 100 milliamps, 7 ohms) In reverse bias, however, a zener diode conducts at a different voltage. This is what zener diodes do. Using Ohm's law, you will get a different effective resistance of the diode in reverse bias, because it is dropping a different voltage. (Example: 5.6 volts, 100 milliamps, 56 ohms) It should be noted that attempting to measure the resistance of a diode does not make sense, because it is a non linear device. You should instead consider the current to voltage curve to understand the diode, be it regular or be it zener.