A Zener diode voltage regulator operated in the range $120 \mathrm{~V}-180 \mathrm{~V}$ produces a constant…

A Zener diode voltage regulator operated in the range $120 \mathrm{~V}-180 \mathrm{~V}$ produces a constant supply of $110 \mathrm{~V}$ and $250 \mathrm{~mA}$ 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
  1. $R_L=280 \Omega, R_S=70 \Omega$
  2. $R_L=440 \Omega, R_S=140 \Omega$
  3. $R_L=70 \Omega, R_S=280 \Omega$
  4. $R_L=440 \Omega, R_S=1400 \Omega$

Solution


We have, $R_L=\frac{V_L}{I_L}=\frac{110}{250 \times 10^{-3}}=440 \Omega$ As current is equally shared by Zener diode and resistance $R$. So, $I_Z=250 \mathrm{~mA}$ Then, $I=2 \times 250=500 \mathrm{~mA} \quad\left[\because I=I_L+I_Z\right]$ $=0.5 \mathrm{~mA}$ So, $\quad R_S=\frac{V_S}{I}=\frac{(180-110)}{0.5}=\frac{70}{0.5}=140 \Omega$ $[\because$ when current is maximum $V=180 \mathrm{~V}]$

Asked in: AP EAMCET 2017 (26 Apr Shift 1)

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