A: You want to build a spot welding machine that need >= 100J capacitor discharge per shot. You have a box full of 25V, 30 mF capacitors. How many capacitors do you need minimun to have enought energy?
B: You chanrge your capacitor above by connecting them to a non-ideal 30-Volt source with a Thevanin resistance of 5 ohm. Since you are careful not to go above the capacitor 25-V rating, design a circuit that can charge your capacitor safely at 25V (drawing should include the source).