Question

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 $9.1 \times 10^{-31}\, kg$ and $\left.1.6 \times 10^{-19} C \right)$.

• A. $- 5.6 \times10^{-11} N/C$
• B. $- 4. 8 \times10^{-15} N/C$
• C. $- 1. 6 \times10^{-19} N/C$
• D. $- 3. 2 \times10^{-19} N/C$

Answer 1

Answer: (A)

$- eE = mg$
$\vec{E} = - \frac{9.1 \times10^{-13}\times10}{1.6 \times10^{-19} } $
$= - 5.6 \times10^{-11} N/C$