Magsafe "L" light takes few seconds before turning off after being unplugged
Solution 1:
It's nothing more than capacitor discharge.
The larger the capacitance, the longer it takes to dissipate once the power source is removed.
It's a power smoothing feature, not just in laptop chargers but many other electrical items.
Without it, small power fluctuations in the mains would cause computer glitches or crashes - or in simpler structures like LED lighting, flickering.