Question

A Zener diode voltage regulator operated in the range $120\, V -180\, V$ produces a constant supply of $110\, V$ and $250\, mA$ to the load. If the maximum current is equally shared between the load and the Zener diode, then the values of load resistance $\left(R_{L}\right)$ and series resistance $\left(R_{S}\right)$ are respectively

• A. $R_{L}=280\, \Omega, R_{S}=70\, \Omega$
• B. $R_{L}=440\, \Omega, R_{S}=140\, \Omega$
• C. $R_{L}=70\, \Omega, R_{S}=280\, \Omega$
• D. $R_{L}=440\, \Omega, R_{S}=1400\, \Omega$

Answer 1

Answer: (B)

$R_{L}=\frac{V_{L}}{I_{I .}}=\frac{110}{250 \times 10^{-3}}=440\, \Omega$
As current is equally shared by Zener diode and resistance $R$.
Then, $I=2 \times 250=500\, mA$
$=0.5\, A$
So, $R_{S}=\frac{V_{S}}{I}=\frac{(180-110)}{0.5}$
$=\frac{70}{0.5}=140\, \Omega$