Fact 1: Aswitch is used to start the flow of current in an electrical circuit.

Fact 2: With switch closed, electricity flows through wires, switch and bulb, to light up the bulb.

Given the two facts above, answer the question "What powers a light bulb?" with the following options: 
- structure and function
 - The tungsten filament
 - photosynthetic pigments?
 - Unplugging a lamp
 - heat production
 - heat is produced
 - Unscrewing a light bulb
 - The flow of electrical current


 

        The flow of electrical current 