The magnitude of the average… - JEE Main 2014 Physics PYQ

JEE Main 2014 — Physics Electromagnetism

2014mcqmedium

The magnitude of the average electric field normally present in the atmosphere just above the surface of the Earth is about $150N/C$ , directed inward towards the center of the Earth. This gives the total net surface charge carried by the Earth to be : [Given : ${\in }_{\text{O}} = \text{8.85} \times 1 {0}^{ - 1 2 } {\text{ C}}^{2} / {\text{N-m}}^{2} \text{, } {\text{R}}_{\text{E}} = \text{6.37} \times 1 {0}^{6} \text{m}$ ]

Official previous-year question

Held on 9 Apr 2014 · Verified 6 Jul 2026.

Options

A
$-680\mathrm{kC}$
B
$+670kC$
C
$+680\mathrm{kC}$
D
$-670\mathrm{kC}$

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Solution

$E=150N/C$

We know that $\phi = \vec{\text{E}} \cdot \vec{\text{A}}$

$= \text{E} \times 4 \pi {\text{r}}^{2}$

$= 1 5 0 \times 4 \pi \times ( ){({\text{R}}_{\text{e}})}^{( ) }$

Now, $\phi = \frac{{\text{Q}}_{\text{in}}}{ }$

JEE Main 2014 Physics, Electrostatics — solution figure

${\text{Q}}_{\text{in}} = \phi {\in }_{\text{o}} = 1 5 0 \times 4 \pi ( ){({\text{R}}_{\text{e}})}^{( ) } \times \text{8.85} \times 1 {0}^{ } \text{C}$

$= 1 5 0 \times 4 \pi { }{{\text{6.37} \times 1 {0}^{6}}}^{{ } } \times \text{8.85} \times 1 {0}^{ }$

$= 6 0 0 \pi \times \text{6.37} \times \text{6.37} \times \text{8.85} C$

$= 6 8 0 \text{kC}$

As Electric field is inward, $Q$ will be negative

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Solution

$E=150N/C$

We know that $\phi = \vec{\text{E}} \cdot \vec{\text{A}}$

$= \text{E} \times 4 \pi {\text{r}}^{2}$

$= 1 5 0 \times 4 \pi \times ( ){({\text{R}}_{\text{e}})}^{( ) }$

Now, $\phi = \frac{{\text{Q}}_{\text{in}}}{ }$

JEE Main 2014 Physics, Electrostatics — solution figure

${\text{Q}}_{\text{in}} = \phi {\in }_{\text{o}} = 1 5 0 \times 4 \pi ( ){({\text{R}}_{\text{e}})}^{( ) } \times \text{8.85} \times 1 {0}^{ } \text{C}$

$= 1 5 0 \times 4 \pi { }{{\text{6.37} \times 1 {0}^{6}}}^{{ } } \times \text{8.85} \times 1 {0}^{ }$

$= 6 0 0 \pi \times \text{6.37} \times \text{6.37} \times \text{8.85} C$

$= 6 8 0 \text{kC}$

As Electric field is inward, $Q$ will be negative

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Options

Did you get this right?

Solution

Your note

JEE Main Electromagnetism in other years

More JEE Main Electromagnetism questions

Other Physics topics for JEE Main

Mechanics

Modern Physics

Optics

Thermodynamics

Waves & Oscillations

Keep practicing Electromagnetism