A-LevelPhysicsD.C. circuitsFeb/Mar 2019Paper 1 Q361 Mark
A cell of internal resistance r and electromotive force (e.m.f.) E is connected in series with a resistor of resistance R. [Figure 36.1] The resistance R and the e.m.f. E remain fixed. The internal resistance r of the cell changes over time. Which graph best shows the variation of the current I in the circuit with the internal resistance r?
A[Graph A: I vs r, current decreases as r increases, with the curve flattening out (concave up).]
B[Graph B: I vs r, current decreases as r increases, with the curve getting steeper (concave down).]
C[Graph C: I vs r, current decreases linearly as r increases.]
D[Graph D: I vs r, current is constant for a while, then decreases as r increases.]
✓ Correct Answer
The correct answer is B. This question tests the candidate's understanding of d.c. circuits within the Physicssyllabus. The examiner's mark scheme requires...
📋 Examiner Report & Trap Analysis
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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