What you're seeing

Each box stores electric charge. Every dot is a bit of charge. Both boxes are charged to the same voltage.

Look at how crowded the dots are. That crowding is the voltage. It's the same in both boxes. Now count the dots. That's the charge. The bigger box has more.

Press Light the bulbs. The switches close and charge flows through each bulb. For two seconds the clock is held at the moment the switches close, so you can compare the bulbs. Check the watts: they match.

Then charge drains out. The dots thin out, the voltage drops, and each bulb dims. The bulb on the smaller box runs out first.

Things to try

Make both boxes the same size. The bulbs behave exactly alike.

Double the voltage. Both bulbs start brighter, and the dots get more crowded in both boxes.

Make Box A three times bigger than Box B. Does its bulb stay lit three times as long?

Switch to Full to see stored energy and a graph of each bulb's power.

What this leaves out

A real bulb's filament changes resistance as it heats up. Here each bulb is treated as a fixed resistance. The fade looks about the same; the exact numbers wouldn't be.

Boxes this big would be supercapacitors. Values are picked so the fade takes seconds, not a blink.

No sparks. How far a spark jumps depends on voltage, not charge, so both boxes would spark the same.