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title: "An ideal battery with potential difference \\(\\Delta V\\) is connected in a circuit with three identical lightbulbs labeled \\(X\\), \\(Y\\), and \\(Z\\), each of resistance \\(R\\), and a switch \\(S\\), as shown. Bulb \\(X\\) is located in the main branch, while bulbs \\(Y\\) and \\(Z\\) are in parallel branches, with switch \\(S\\) in series with bulb \\(Z\\). Switch \\(S\\) is initially closed and is then opened. Which of the following correctly ranks the brightness of the three bulbs after switch \\(S\\) is opened?"
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url: "https://nerd-notes.com/ubq/117523/"
date_modified: "2026-08-04T06:52:39+00:00"
---

# An ideal battery with potential difference \(\Delta V\) is connected in a circuit with three identical lightbulbs labeled \(X\), \(Y\), and \(Z\), each of resistance \(R\), and a switch \(S\), as shown. Bulb \(X\) is located in the main branch, while bulbs \(Y\) and \(Z\) are in parallel branches, with switch \(S\) in series with bulb \(Z\). Switch \(S\) is initially closed and is then opened. Which of the following correctly ranks the brightness of the three bulbs after switch \(S\) is opened?

An ideal battery with potential difference \(\Delta V\) is connected in a circuit with three identical lightbulbs labeled \(X\), \(Y\), and \(Z\), each of resistance \(R\), and a switch \(S\), as shown. Bulb \(X\) is located in the main branch, while bulbs \(Y\) and \(Z\) are in parallel branches, with switch \(S\) in series with bulb \(Z\). Switch \(S\) is initially closed and is then opened. Which of the following correctly ranks the brightness of the three bulbs after switch \(S\) is opened?

![A rectangular circuit schematic diagram is drawn with clean dark lines on a white background. On the left vertical wire, an ideal battery symbol is drawn with the longer positive plate at top, labeled with potential difference \(\Delta V\). The top horizontal wire extends to the right and connects to a lightbulb symbol labeled X. After bulb X, the wire splits at a T-junction into two parallel vertical branches extending downward. The left parallel branch contains a lightbulb symbol labeled Y. The right parallel branch contains a lightbulb symbol labeled Z in series with an open switch symbol labeled S. Below the parallel branches, the wires recombine at a bottom T-junction into a single bottom horizontal wire that returns to the negative terminal of the battery. No other labels, lines, text, or components appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1785826359-83HqIZ.jpg)

- **A.** \(P_X = P_Y > P_Z\)
- **B.** \(P_X > P_Y > P_Z\)
- **C.** \(P_X > P_Y = P_Z\)
- **D.** \(P_Z > P_X = P_Y\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/117523/*