Question

Calculate the electric field strength required to just support a water drop of mass ${10}^{-7}kg$ having a charge $1.6\times {10}^{-19}C$.

• A. $4.125\times {10}^{12}N{C}^{-1}$
• B. $3.125\times {10}^{12}N{C}^{-1}$
• C. $6.125\times {10}^{12}N{C}^{-1}$
• D. $2.125\times {10}^{12}N{C}^{-1}$

Answer 1

The correct option is C $6.125\times {10}^{12}N{C}^{-1}$

For equilibrium of drop, electric force should be equal to weight.

$qE=mg$

$⟹E=\frac{mg}{q}$

$⟹E=\frac{{10}^{-7}\times 9.8}{1.6\times {10}^{-19}}$

$⟹E=6.125\times {10}^{12}N{C}^{-1}$

Answer-(C)