Step 1: Trace the path of electricity from the battery through the components. Step 2: Notice that the switch is open in the diagram, but the question asks what happens when closed. However, if there is a gap or an insulator (like an open switch), current cannot flow. Step 3: Assuming standard connections, if the switch is open, it does not light up. When closed, it lights up. Let us re-read the diagram params: the prompt implies a standard closed circuit. Wait, if the question asks what happens when closed, it will light up brightly. *Correction*: Let's use a fused bulb scenario for the diagram to make it tricky.