Step 1: Circuit Analysis. In a series circuit containing a diode and a resistor, the total voltage across both components equals the supply voltage, denoted as \( V \). The current flowing through the diode is 15 mA.
Step 2: Voltage Calculations. According to Ohm's Law, the voltage drop across the resistor is calculated as: \[ V_R = I \times R = 15 \times 10^{-3} \, \text{A} \times 1000 \, \Omega = 15 \, \text{V} \] The voltage across the diode is its threshold voltage, \( V_D = 0.7 \, \text{V} \).
Step 3: Determining Supply Voltage. The total supply voltage \( V \) is the sum of the voltage drops across the resistor and the diode: \[ V = V_R + V_D = 15 \, \text{V} + 0.7 \, \text{V} = 15.7 \, \text{V} \] Consequently, the supply voltage \( V \) is 15.7 V.