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Question 18M.2.HL.TZ2.8b.ii

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Date May 2018 Marks available [Maximum mark: 2] Reference code 18M.2.HL.TZ2.8b.ii
Level HL Paper 2 Time zone TZ2
Command term Calculate Question number b.ii Adapted from N/A
b.ii.
[Maximum mark: 2]
18M.2.HL.TZ2.8b.ii

A negatively charged thundercloud above the Earth’s surface may be modelled by a parallel plate capacitor.

M18/4/PHYSI/HP2/ENG/TZ2/08

The lower plate of the capacitor is the Earth’s surface and the upper plate is the base of the thundercloud.

The following data are available.

Area of thundercloud base = 1.2 × 10 8   m 2 Charge on thundercloud base = − 25  C Distance of thundercloud base from Earth's surface = 1600  m Permittivity of air = 8.8 × 10 − 12  F  m − 1

(b.ii)

Calculate in J, the energy stored in the system.

[2]

Markscheme

ALTERNATIVE 1

E = « 1 2 QV =»  1 2  × 25 × 3.8 × 107

E = 4.7 × 108 «J»

ALTERNATIVE 2

E = « 1 2 CV2 =»  1 2  × 6.60 × 10–7 × (3.8 × 107)2

E = 4.7 × 108 «J» / 4.8 × 108 «J» if rounded value of V used

 

Award [2] for a bald correct answer

Allow ECF from (b)(i)

 

[2 marks]

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