---
title: "A real battery with electromotive force (emf) \\(\\varepsilon\\) and constant internal resistance \\(r\\) is connected in series with a variable resistor of resistance \\(R\\), as shown in the diagram. An experimenter slowly decreases the resistance \\(R\\), which causes the current \\(I\\) in the circuit to increase. Which of the following statements correctly describes what happens to the terminal voltage across the battery and provides the correct justification?"
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url: "https://nerd-notes.com/ubq/120379/"
date_modified: "2026-08-23T04:34:23+00:00"
---

# A real battery with electromotive force (emf) \(\varepsilon\) and constant internal resistance \(r\) is connected in series with a variable resistor of resistance \(R\), as shown in the diagram. An experimenter slowly decreases the resistance \(R\), which causes the current \(I\) in the circuit to increase. Which of the following statements correctly describes what happens to the terminal voltage across the battery and provides the correct justification?

A real battery with electromotive force (emf) \(\varepsilon\) and constant internal resistance \(r\) is connected in series with a variable resistor of resistance \(R\), as shown in the diagram. An experimenter slowly decreases the resistance \(R\), which causes the current \(I\) in the circuit to increase. Which of the following statements correctly describes what happens to the terminal voltage across the battery and provides the correct justification?

![A single rectangular circuit schematic. Along the top horizontal branch, a dashed rectangular box represents a real battery. Inside the dashed box, an ideal battery symbol with two parallel vertical plates of unequal length labeled \(\varepsilon\) is wired in series with a resistor symbol labeled \(r\). Solid dots labeled \(X\) and \(Y\) mark the terminals on the wire just outside the left and right ends of the dashed box. A voltmeter circle labeled \(V\) is connected in parallel across terminals \(X\) and \(Y\). The circuit continues clockwise down the right vertical wire to the bottom horizontal branch. The bottom branch contains a variable resistor symbol, shown as a standard zig-zag resistor with a diagonal arrow passing through it, labeled \(R\). The left vertical wire connects back to terminal \(X\) to complete the loop. An arrow above the top wire labeled \(I\) points to the right. No other labels, lines, text, or components appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1787459662-5AX4Qf.jpg)

- **A.** The terminal voltage remains constant because the battery maintains a constant electromotive force \(\varepsilon\) determined solely by its internal chemical reactions.
- **B.** The terminal voltage increases because the increased current delivers electric potential energy to the circuit at a greater overall rate.
- **C.** The terminal voltage decreases because the greater current produces a larger potential difference across the internal resistance of the battery.
- **D.** The terminal voltage decreases because the internal resistance of the battery increases proportionally as more charge flows through it.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/120379/*