Question

A zener diode having zener voltage 8 V and power dissipation rating of 0.5 W is connected across a potential divider arranged with maximum potential drop across zener diode is as shown in the diagram. The value of protective resistance R_p is ...........Ω.

Answer 1

Answer is 192

P = Vi

0.5 = 8i

i = \(\cfrac1{16}\)A

E = 20 = 8 + i R_P

R_P = 12 x 16 = 192 Ω