A-LevelPhysicsD.C. circuits9702/12 · Oct/Nov 2019 · Q341 Mark

Two cells with electromotive forces E₁ and E₂ and internal resistances r₁ and r₂ are connected to a resistor R as shown. [Figure showing two cells E₁ with r₁ and E₂ with r₂ connected in series with an external resistor R, with a current arrow.] The terminal potential difference across cell 1 is zero. Which expression gives the resistance of resistor R?

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A(E₂r₁ − E₁r₂) / E₁

B(E₂r₁ − E₁r₂) / E₂

C(E₁r₂ − E₂r₁) / E₁

D(E₁r₂ − E₂r₁) / E₂

✓ Correct answer

A: (E₂r₁ − E₁r₂) / E₁

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Topic: D.C. circuits, A-Level Physics (syllabus 9702). Multiple choice, 1 mark.
Source: A-Level Physics, Oct/Nov 2019 Paper 1 Variant 2, question 34.

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