I just installed a dimmer for a set of (non-dimmable) MR16 bulbs wired in parallel. The dimmer sits between a 12V power supply and the bulbs.
My observation when trying to dim the non-dimmable bulbs is that the brightness stays the same until the input voltage to the bulbs drops to below roughly 1V. Then the brightness drops rapidly.
I suspected that the bulbs were drawing more current in order to compensate for the drop in input voltage in order to keep the amount of power drawn the same. So I measured it, they weren't.
So therefore I know that as input voltage drops from 12V to 6V the power drawn by each bulb drops, but I also know the apparent brightness of the bulbs does not. I can only conclude that the extra power drawn from a bulb run at 12V must be dissipated as heat.
My question is: is my conclusion correct? Is there a reason to run my bulbs at 12V or is 3V good enough? Will running the bulbs at a lower voltage lengthen their life? Is there a simple (UK A-Level / US High-School-Diploma) circuit diagram that can explain the behaviour and be used to calculate how much power is converted into heat?