The 6 V Zener diode shown in the figure has negligible resistance and a knee current of 5 mA . The minimum value of R in Ω so that the voltage across it does not fall below 6 V is

Step-by-step solution

In Zener diode, ⇒    V max - V Z R 1 ≥ I knee + I R R 1 is the series resistance of 50   Ω and I R is the current through the resistance R ⇒    10 - 6 50 ≥ 5 m + I R ⇒   I R ≤ 80   mA - 5   mA ∵ I R max = 75   mA (the maximum current through R ) So the minimum value of the resistance R is R min = V I R max = 6   V 75   mA = 6000 75 = 80   Ω