A basic question on Current Flow, Voltage, and Power consumption
For a bulb to glow all it cares for is the flow of electrons at the required rate (amps).


Correct, if the filament gauge remains constant.


  Assume that I keep the current constant at 2 amps by reducing both the voltage and resistance.


Reducing the voltage isn't a problem. Reducing the resistance is because you need to shorten the filament length.

If you could make a filament lamp with variable length filament you would get constant brightness per unit length. Total brightness would, of course, drop. Try it and see ...







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. 'Bulb' with variable filament length.

In Figure 1 we've created a lamp with variable filament length. You can adjust the filament resistance by switching out lamps as you step down the voltage.


  "For a bulb to glow all it cares for is the flow of electrons at the required rate (amps)", shouldn't the bulb remain bright?


Yes, the filament temperature will remain the same, the light spectrum emitted will be the same and the light emitted per unit length will be the same. There will just be less of it overall.