y13 Questions on magnetism and Universe
1. (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
(iii) F = Bev allow BQv 1
(iv) F = mv2/r; Bev = mv2/r; (2)
B = mv/er = 1.67 × 10–27 × 1.5 × 107/(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]
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
[3]
3. (a) Positive as E-field is downwards/top plate is positive/like charges repel/AW (1) 1
(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
(c) E = V/d; so d = V/E = 600/4 × 104 = 0.015 m (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
[13]
4. Any four from:
Uniform intensity in all directions / everywhere
Structure in background intensity / ripples
Produced when matter and radiation decoupled
Originally gamma radiation
(gamma) red-shifted to microwave / originally higher energy
Evidence that universe began with big bang
Temperature corresponds to 2.7 K / 3K / that predicted by big bang model B1 × 4
Link between evidence and explanation. (1)
[5]
5. Any 5 from
red shift data for galaxies (accept stars) 1
calculate velocity from red shift 1
galaxies/ stars receding from Earth 1
distance data for galaxies/ stars 1
velocity α distance / v/r = constant / v-r graph straight line 1
universe began at a single point 1
[5]
6. (a) Any two
stars rotate around galactic centre 1
star with velocity component towards Earth 1
reference to motion/shape of galaxy 1
or other valid points eg blue shift
(b) Ho = 75/ 3 × 1019 s–1 1
t ≈ 1/ 2.5 × 10–18 1
t ≈ 4 × 1017 s 1
[5]
