DP Physics (last assessment 2024)

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

Date	May 2018	Marks available	[Maximum mark: 1]	Reference code	18M.2.HL.TZ2.8c.ii
Level	HL	Paper	2	Time zone	TZ2
Command term	Calculate	Question number	c.ii	Adapted from	N/A

c.ii.

[Maximum mark: 1]

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

$\begin{array}{*{20}{l}} {{\text{Area of thundercloud base}}}&{ = 1.2 \times {{10}^8}{\text{ }}{{\text{m}}^2}} \\ {{\text{Charge on thundercloud base}}}&{ = -25{\text{ C}}} \\ {{\text{Distance of thundercloud base from Earth's surface}}}&{ = 1600{\text{ m}}} \\ {{\text{Permittivity of air}}}&{ = 8.8 \times {{10}^{ - 12}}{\text{ F }}{{\text{m}}^{ - 1}}} \end{array}$

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.ii)

Calculate, in A, the average current during the discharge.

[1]

Markscheme

I «= $\frac{{\Delta Q}}{{\Delta t}} = \frac{{11}}{{18 \times {{10}^{ - 3}}}}$ » ≈ 610 «A»

Accept an answer in the range 597 − 611 «A»

[1 mark]

Syllabus sections

Core

Core » Topic 5: Electricity and magnetism » 5.1 – Electric fields

Core » Topic 5: Electricity and magnetism

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

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