The diagram below is verbally described; you may draw your own sketch to aid your work.
Circuit description:
• A 6.0V battery has its positive terminal connected to point M.
• From M, two parallel branches extend to point N.
– Branch 1 contains a resistor R1 of 15Ω.
– Branch 2 contains an ideal copper wire of negligible resistance.
• From point N, the circuit continues through a single–pole switch K to point O, then through resistor R2 of 30Ω before returning to the negative terminal of the battery.
Assume the switch is initially open.
(a) Identify the electrical state of the entire circuit while switch K remains open. Support your answer with reference to the definitions of open circuit and closed loop.
(b) When K is closed, determine whether R1 and R2 experience any potential difference. Classify the resulting condition of each element (normal operation, bypassed by short, or part of an open circuit) and explain your reasoning.
(c) For the switch–closed case, calculate the current delivered by the battery. Show your reasoning step by step and include units.
(d) Suppose the ideal wire in Branch 2 is replaced by another resistor R3=5.0Ω. Qualitatively describe how the circuit state and battery current would change compared to part (c). No numerical calculation is required.