When you depress the switch, a piece of metal in the switch completes the circuit so electricity can flow from one end of the battery to the other end.
(you; depress; the switch) (a piece of metal in the switch; completes; the circuit; T:When you depress the switch) (electricity; can flow; from one end of the battery to the other end)
you a piece of metal in the switch electricity
depress completes can flow
the switch
the circuit T:When you depress the switch
from one end of the battery to the other end