Question

If the mass of the electron is $9.1\times {10}^{-31}\text{kg}$ and Charge its charge is $1.6\times {10}^{-19}\text{C}$ , then the intensity of the electric field required to balance the weight of an electron is

• A. $5.6\times {10}^{-9}\text{N/C}$
• B. $5.6\times {10}^{-11}\text{N/C}$
• C. $5.6\times {10}^{-8}\text{N/C}$
• D. $5.6\times {10}^{-7}\text{N/C}$

Answer 1

The correct option is B $5.6\times {10}^{-11}\text{N/C}$

Given :
$m_e=9.1\times {10}^{–31}\text{kg}$ and $q_e=1.6\times {10}^{–19}\text{C}$

At equilibrium, the electric force balances the weight of electrons.
$\therefore qE=mg$

$\Rightarrow E=\frac{mg}{q}=\frac{9.1\times {10}^{-31}\times 9.8}{1.6\times {10}^{-19}}$

$\Rightarrow E=5.6\times {10}^{-11}\text{N/C}$

Hence, option (b) is the correct answer.