Circuit Fundamentals — question 10 of 10
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Classic inductive-kickback scenario when switching an inductive load without protection.
A relay coil is modeled as 100mH of inductance in series with 10 ohms of resistance, carrying 500mA, driven through a MOSFET switch with no flyback diode across the coil. When the MOSFET abruptly turns off, the textbook formula V = L(di/dt) suggests the voltage spike across the switch node could be enormous, even unbounded. Explain what's physically wrong with taking that formula at face value here, what actually limits the real voltage spike in hardware, and what you'd add to the circuit to fix it.