DP Physics (last assessment 2024)

Test builder »

Question 18M.2.HL.TZ2.8c.i

Select a Test
Date May 2018 Marks available [Maximum mark: 3] Reference code 18M.2.HL.TZ2.8c.i
Level HL Paper 2 Time zone TZ2
Command term Show that Question number c.i Adapted from N/A
c.i.
[Maximum mark: 3]
18M.2.HL.TZ2.8c.i

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

Lightning takes place when the capacitor discharges through the air between the thundercloud and the Earth’s surface. The time constant of the system is 32 ms. A lightning strike lasts for 18 ms.

(c.i)

Show that about –11 C of charge is delivered to the Earth’s surface.

[3]

Markscheme

Q = « Q 0 e − t τ  =» 25 × e − 18 32

Q = 14.2 «C»

charge delivered = Q = 25 – 14.2 = 10.8 «C»

«≈ –11 C»

 

Final answer must be given to at least 3 significant figures

[3 marks]

Syllabus sections