Potentiometer

Compare EMFs by null deflection.

Concept

Potentiometer is a foundational idea in this chapter. The defining relationship is:

$\varepsilon_1/\varepsilon_2 = l_1/l_2$

Crucially, no current is drawn at balance — measures true EMF, not terminal V.

Worked Application

Apply the formula to a typical problem from your textbook. Identify the knowns, plug into the equation, and check that the units work out. Always sanity-check the magnitude before accepting an answer.

Common Confusions

• Confusing the variables in the formula — re-read the symbol definitions in the chapter.
• Forgetting unit conversions (cm vs m, g vs kg).
• Ignoring sign conventions where direction matters.

Key Takeaways

• Master the formula $\varepsilon_1/\varepsilon_2 = l_1/l_2$ and one canonical example.
• See the chapter index for full derivations, traps and exam-grade problems.