Question

the mass of an electron is 9.11x10^-31 kg. charge on the electrcon is 1.69x10^-19 C and g = 9.8 m/s^2 then the intensity of eletric field required to balance weight of an electron is?

Answer 1

The weight of electron is:

$$P = mg$$

where $m = 9.11\times 10^{-31}kg$ and $g = 9.8 m/s^2$.

The electric force acting on electron in the field $E$ is the following:

$$F = qE$$

where $q = 1.69\times 10^{-19}C$. The balance condition:

$$P = F\\ mg = qE\\$$

Expressing the intensity of eletric field, obtain:

$$E = \dfrac{mg}{q} = \dfrac{9.11\times 10^{-31}\cdot 9.8}{1.69\times 10^{-19}} \approx 5.28 \times10^{-11} N/q$$

Answer. 5.28x10^-11 N/q.