A-LevelPhysicsMagnetic fieldsFeb/Mar 2018Paper 4 Q108 Marks
(a) (i) Define magnetic flux. (ii) State Faraday's law of electromagnetic induction. (b) A solenoid has a coil C of wire wound tightly about its centre, as shown in [Figure 10.1]. The coil C has 96 turns. The uniform magnetic flux Φ (in weber) in the solenoid is given by the expression Φ = 6.8 × 10⁻⁶ × I where I is the current (in amperes) in the solenoid. Calculate the average electromotive force (e.m.f.) induced in coil C when a current of 3.5 A is reversed in the solenoid in a time of 2.4 ms. e.m.f. = .............................................................. V (c) The d.c. supply in [Figure 10.1] is now replaced with a sinusoidal alternating supply. Describe qualitatively the e.m.f. that is now induced in coil C.
📋 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...
🎯 Mark Scheme Breakdown
Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.
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