A student builds a miniature holiday light string consisting of a 9.0V battery, two identical incandescent bulbs (labeled Bulb X and Bulb Y), and a single–pole switch S that can connect either point A or point B to node N as shown in the description below.
Textual description of the circuit:
1. The positive terminal of the battery is connected to node P.
2. From node P, one branch leads through Bulb X to node Q. A second, separate branch runs directly from P to node Q with no components in between.
3. Node Q is connected to node N by an ordinary conducting wire.
4. Switch S has a movable arm that can connect node N to either point A or point B.
• When the arm touches point A, current must pass through Bulb Y on its way from N to the negative terminal of the battery.
• Point B is connected directly to the negative terminal of the battery by a wire with negligible resistance.
5. All wires are ideal conductors unless stated otherwise.
(a) Describe, without calculation, the electrical state of the circuit (open, closed, or short) when the switch arm touches point A. Explain how this state affects the operation of Bulb X and Bulb Y.
(b) Repeat part (a) for the case in which the switch arm touches point B.
(c) The student claims that in one of the switch positions the circuit forms multiple closed loops simultaneously. Identify which position this is and justify whether the claim is correct, referencing the definition of a closed loop.
(d) Suppose Bulb Y fails and becomes an open element (the filament breaks) while the switch is still touching point A. Predict the resulting state of the circuit and describe what happens to Bulb X. Provide reasoning that connects the physical arrangement to potential difference across Bulb X.