Question

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

• A. $1.5\Omega$
• B. $5\Omega$
• C. $6.6\Omega$
• D. $20\Omega$

Answer 1

The correct option is B $5\Omega$

Given,

$P_{max}=100\text{mW}\text{Voltage drop across diode}=0.5\text{V}\text{Supply voltage}=1.5\text{V}$

$\because P=VI$

Current flow through the circuit is, $I=\frac{P}{V}$

$I=\frac{100\times {10}^{-3}}{0.5}=0.2\text{A}$

Now, the voltage drop across the resistance $\left(R\right)$ is,

$V_R=1.5–0.5=1\text{V}$

$V_R=IR$

$1=0.2R$

$R=5\Omega$

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Hence, $\left(B\right)$ is the correct answer.