Question

The diode used in the circuit shown in the figure has a constant voltage drop of 0.5V at all currents and a maximum power rating 100mW. What should be the value of the resistor R connected in series with the diode for obtaining maximum current


A) 1.5 ohm
B) 5 ohm
C) 6.67 ohm
D) 200 ohm

Answer 1

the maximum current flows in the circuit will be the option b which is 5ohm

Answer 2

The resistor value of R is 5 ohm which is in series with diode.

Solution:

The diode with constant voltage drop at all current and has maximum power rating as 100 mW. The resistance at maximum current will be calculated by –

Given: Voltage drop = 0.5 V

Power rating max = 100 m W = 0.1 W

Emf E = 1.5 V

Thereby as we know that P=$I \times V_{d}$

$\begin{aligned} I &=\frac{P}{V_{d}} \\ I &=\frac{0.1}{0.5} \\ I &=0.2 \mathrm{A} \\ V &=E-V_{d} \\ V &=1.5-0.5 \end{aligned}$

$\begin{aligned} V &=1 V \\ V &=I \times R \\ R &=\frac{V}{I} \\ R &=\frac{1}{0.2} \\ R &=5 \text { ohm } \end{aligned}$