Question

In the oil drop experimant, charge on electron came out to be $-1.6\times {10}^{-19}\text{C}$. From Thomson's experiment, $e/m$ value for electron calculated was $1.758820\times {10}^{11}\text{C/kg}$. Find the mass of the electron.
(Given: $e$ is the magnitude of charge on electron)

• A. $1.67\times {10}^{-27}\text{kg}$
• B. $9.1\times {10}^{-31}\text{kg}$
• C. $9.1\times {10}^{-28}\text{kg}$
• D. $1.67\times {10}^{-31}\text{kg}$

Answer 1

The correct option is B $9.1\times {10}^{-31}\text{kg}$

Charge on electron $=-1.6\times {10}^{-19}\text{C}$
Value of $\frac{e}{m}=1.758820\times {10}^{11}\text{C/kg}$
$\text{Mass of}{e}^{-}=\frac{\text{Magnitude of charge on}{e}^{-}}{\frac{e}{m}}$

$=\frac{1.6\times {10}^{-19}\text{C}}{1.758820\times {10}^{11}\text{C/kg}}$

$\approx 9.1\times {10}^{-31}\text{kg}$