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Four resistors and an open switch S are connected to a battery of unknown emf ε in the circuit shown above. The switch is initially open. Which of the following is true about the potential across the 18 Ω resistor after the switch is closed?

It decreases because initially the 6â€‰Î© and 18â€‰Î© resistors split the battery emf proportionally, and afterward the 6â€‰Î© and 18â€‰Î© resistors split the battery emf evenly.
It increases because the total resistance of the circuit decreases.
It remains the same because the ratio of the 6â€‰Î© and 18â€‰Î© resistances is the same as the ratio: equivalentâ€‰resistanceâ€‰ofâ€‰3â€‰Î©â€‰andâ€‰6â€‰Î©â€‰resistors/equivalentâ€‰resistanceâ€‰ofâ€‰9â€‰Î©â€‰andâ€‰18â€‰Î©â€‰resistors.
It decreases because initially the 6â€‰Î© and 18â€‰Î© resistors split the battery emf, and afterward the 9â€‰Î© and 18â€‰Î© resistors split the battery emf.

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