To find the series resistance (Rs) for the given circuit with three 10V zener diodes in series, you can use the following formula:
\[ Rs = \frac{V_{\text{source}} - n \cdot V_{\text{zener}}}{I_{\text{zener}}} \]
where:
- \( V_{\text{source}} \) is the source voltage (45 volts in this case),
- \( n \) is the number of zener diodes in series (3 in this case),
- \( V_{\text{zener}} \) is the zener voltage of one diode (10 volts in this case),
- \( I_{\text{zener}} \) is the zener current (1000mA or 1A in this case).
Substitute the values into the formula to find Rs:
\[ Rs = \frac{45 - 3 \cdot 10}{1} = \frac{45 - 30}{1} = 15 \, \Omega \]
So, the series resistance required is 15 ohms.
