Concept:By Kirchhoff's Voltage Law (KVL), the total supply voltage in a series diode circuit equals the sum of the forward voltage drop across the diode and the voltage drop across the current-limiting resistor.
Formula:$$V_{\text{source}} = V_D + I R \implies I = \frac{V_{\text{source}} - V_D}{R}$$
Solution:- Given values: \(V_{\text{source}} = 5.0\text{ V}\), \(V_D = 0.7\text{ V}\), \(R = 200\,\Omega\).
- Calculate voltage across resistor:
- $$V_R = 5.0\text{ V} - 0.7\text{ V} = 4.3\text{ V}$$
- Calculate circuit current:
- $$I = \frac{4.3\text{ V}}{200\,\Omega} = 0.0215\text{ A} = 21.5\text{ mA}$$
Why other options are incorrect:- Option B: \(25.0\text{ mA}\) is obtained by incorrectly ignoring the diode voltage drop: \(5.0 / 200 = 25\text{ mA}\).
- Option C: \(15.0\text{ mA}\) is an arbitrary calculation error.
- Option D: \(10.0\text{ mA}\) corresponds to an incorrect forward drop calculation.
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