A-LevelPhysicsD.C. circuitsOct/Nov 2019Paper 1 Q351 Mark
A battery has an electromotive force (e.m.f.) E and internal resistance r. The battery delivers a current I to a variable resistor and the potential difference (p.d.) across its terminals is V. [Figure showing a battery with e.m.f. E and internal resistance r connected to a variable resistor, with current I and terminal p.d. V indicated.] The variable resistor is adjusted so that I increases. Why does V decrease?
AThe e.m.f. E decreases.
BThe internal resistance r increases.
CThe p.d. across r increases.
DThe resistance of the variable resistor increases.
✓ Correct Answer
The correct answer is C. This question tests the candidate's understanding of d.c. circuits within the Physicssyllabus. The examiner's mark scheme requires...
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Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
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