JEE Main 2026 — Jan 24, Shift 1 — Physics solution

JEE Main2026Jan 24, Shift 1Physics

A voltage regulating circuit consisting of Zener diode, having break-down voltage of 10 V and maximum power dissipation of 0.4 W, is operated at 15 V. The approximate value of protective resistance in this circuit is ______ $Ω$ .

Your answer

Solution

Maximum current through the Zener:

$i_{m a x} = \frac{P _{m a x}}{V _{Z}} = \frac{0.4}{10} = 0.04$ A.

The protective resistor carries this current and drops the excess voltage ( $V_{supply} - V_{Z} = 15 - 10 = 5$ V):

$R = \frac{V _{supply} - V _{Z}}{i _{m a x}} = \frac{5}{0.04} = 125 Ω$ .

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