Problem 2: A cylindrical capacitor mounted to a circuit board in an AC-to-DC power converter is initially at a uniform temperature of 55°C. The capacitor has a diameter of 1 cm and a length of 1.5 cm, with a density of 5000 kg/m³, a specific heat capacity of 3 kJ/kg-K, and a thermal conductivity of 8 W/m-K. A fan blows air at a velocity of 5 m/s and 20°C past the capacitor. If the power converter is turned off (assume the fan continues to run), how long would it take for the capacitor temperature to drop below 30°C? Ans:9.8 min

Fig: 1