a light bulb is a kind of electrical device & an electrical device requires electricity to turn on ->  a light bulb requires electricity to turn on  an electric circuit is a vehicle for moving electrical energy from the source to the electrical device & when a switch in a simple series circuit is closed , electricity will flow through the circuit ->  when a switch is closed, the electrical energy will flow from the source to the electrical device  when a switch is closed, the electrical energy will flow from the source to the electrical device & a light bulb is a kind of electrical device ->  when a switched is closed, the electrical energy will flow to the light bulb  when a switched is closed, the electrical energy will flow to the light bulb & electricity is a kind of electrical energy ->  when a switch is closed, the electricity will flow to the lightbulb  a light bulb requires electricity to turn on & when a switch is closed, the electricity will flow to the lightbulb -> when electricity flows to a light bulb , the light bulb will turn on / come on