oppose the motionchange that produced it 1 relationship of Lenzs law to

# Oppose the motionchange that produced it 1

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oppose the motion/change that produced it 1 relationship of Lenz’s law to conservation of energy or other valid explanation/discussion/description 2 max 5 marks quality of written communication 2 [7] 4. (a) B = F/Il with symbols explained or appropriate statement in words; (1) explicit reference to I and B at right angles/define from F = BQv etc (1) 2 (b) (i) arrow towards centre of circle 1 (ii) field out of paper; Fleming’s L.H. rule/moving protons act as conventional current 2 PhysicsAndMathsTutor.com 1
(iii) F = Bev allow BQv 1 (iv) F = mv 2 /r; Bev = mv 2 /r; (2) B = mv/er = 1.67 × 10 –27 × 1.5 × 10 7 /(1.6 × 10 –19 × 60); = 0.0026; T (3) 5 allow Wb m –2 (v) the field must be doubled; (1) B v (as m, e and r are fixed)/an increased force is required to maintain the same radius (1) 2 [13] 5. (a) appropriate shape; lines perpendicular to and touching plate and sphere; (2) arrows towards negative sphere (1) 3 (b) (i) By moments, e.g F cos 20 = W sin 20 / by triangle of forces / by resolution of forces / other suitable method; i.e. justification needed (1) F = 1.0 × 10 –5 tan 20; = 1.0 × 10 –5 × 0.364; (= 3.64 × 10 –6 N) (2) triangle of forces gives W/F = tan 70, etc (1) 3 (ii) E = F/Q; = 3.64 × 10 –6 / 1.2 × 10 –9 = 3.0 × 10 3 ;N C –1 / V m –1 3 (c) E = (1/4 πε o )Q/r 2 ; 3.0 × 10 3 = 9 × 10 9 × 1.2 × 10 –9 /r 2 ; (2) or use F = (1/4 πε o )Q 2 /r 2 ; r 2 = 3.6 × 10 –3 giving r = 6 × 10 –2 (m) (1) 3 (d)

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• Spring '18
• fatima
• Force, Magnetic Field, Ambrose College

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