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Tuesday, January 19, 2021

Assessed Homework Electromagnetism

 

1.       (a)     (i)      equally spaced horizontal parallel lines from plate to plate (1)
arrows towards cathode (1)                                                                     2

  (ii)   ½ mv2 = qV; v = √(2eV/m) = √(2 × 1.6 × 10–19 × 7000/9.1 × 10–31) so (1)
v = 4.96 × 107 (m s–1) (1)                                                                        2

  (b)   (i)      arrow perpendicular to path towards centre of arc (1)                             1

(ii)     out of paper/upwards;using Fleming’s LH rule (for conventional
current) (2)                                                                                              2

  (iii)  mv2/r; = Bqv; r = mv/Bq ;= 9.4 × 10–2
(m)                                                                                                          4

  (c)   change magnitude of current in coils to change field; (1)
change field to change deflection; (1)
reverse field/current to change deflection from up to down (1) max 2             2

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  2.     At least 3 field lines inside solenoid parallel to axis; (1)
Lines equally spaced over some of length of solenoid. (1)
Arrows on lines pointing left to right. (1)                                                                   3

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 4.      (i)      I = V/R = 12/50 (1)
= 0.24 A (1)                                                                                                                2

  (ii)   Power in primary = power in secondary / IpVp = IsVs (1)
Ip = 0.24 × 12 / 230 = 0.0125 A (1)                                                                  2

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5.      

  (b)   (i)      k.e. = QV; = 300 × 1.6 × 10–19 = (4.8 × 10–17 J) (2)                                2

  (ii)   1/2mv2 = 4.8 × 10–17; = 0.5 × 2.3 × 10–26 × v2 so v2 = 4.17 × 109;
(giving v = 6.46 × 104 m s–1) (2)                                                             2

                   (d)     (i)         semicircle to right of hole (1) ecf(a); (a) and d(i) to be consistent        1

(ii)     mv2/r; = BQv; (2)
giving r = mv/BQ = 2.3 × 10–26 × 6.5 × 104/(0.17 × 1.6 × 10–19); (1)
r = 55 mm;so distance = 2r = 0.11 m (2)                                                 5

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