Question

In the circuit shown below, determine the current in the resistor. Given: \[ E=10.7\ \text{V} \] \[ R=10\,k\Omega \] Silicon diode in forward bias.

• A. \(1\ \text{mA}\)
• B. \(1.07\ \text{mA}\)
• C. \(0.1\ \text{mA}\)
• D. \(10\ \text{mA}\)

Hint:

For a forward-biased silicon diode, always subtract \[ 0.7\ \text{V} \] from the supply voltage before applying Ohm's law.

Answer 1

The Correct Option is A

Step 1: Treat the diode as a fixed voltage drop.
A silicon diode in forward bias behaves like a small battery that always drops about $0.7$ V across itself. The rest of the supply appears across the resistor.

Step 2: Apply Kirchhoff's voltage law.
Going around the loop, the supply equals the diode drop plus the resistor voltage: \[ E=V_{\text{diode}}+V_R. \]

Step 3: Solve for the resistor voltage.
\[ V_R=E-0.7=10.7-0.7=10\ \text{V}. \]

Step 4: Note the resistance.
$R=10\,\text{k}\Omega=10\times10^3\,\Omega$.

Step 5: Use Ohm's law.
\[ I=\frac{V_R}{R}=\frac{10}{10\times10^3}=10^{-3}\ \text{A}. \]

Step 6: Express in milliamperes.
\[ I=1\ \text{mA}. \]
\[ \boxed{I=1\ \text{mA}} \]