The electric field intensity just sufficient to balance the earth's gravitational attraction on an electron…

The electric field intensity just sufficient to balance the earth's gravitational attraction on an electron will be: (given mass and charge of an electron respectively are $9.1 \times 10^{-31} \mathrm{~kg}$ and $\left.1.6 \times 10^{-19} \mathrm{C} .\right)$
  1. $-5.6 \times 10^{-11} \mathrm{~N} / \mathrm{C}$
  2. $-4.8 \times 10^{-15} \mathrm{~N} / \mathrm{C}$
  3. $-1.6 \times 10^{-19} \mathrm{~N} / \mathrm{C}$
  4. $-3.2 \times 10^{-19} \mathrm{~N} / \mathrm{C}$

Solution

$-\mathrm{eE}=\mathrm{mg}$
$\overrightarrow{\mathrm{E}}=-\frac{9.1 \times 10^{-31} \times 10}{1.6 \times 10^{-19}}=-5.6 \times 10^{-11} \mathrm{~N} / \mathrm{C}$ ,

Asked in: JEE Mains - Electrostatics - Test 2

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