Question

which of the following charges can exist on an oil drop( in millikan oil drop experiment).

(a)3.2 x 10^-19 C
(b)8.3 x 10^19 C
(c)4.8 x 10^-19 C
(d)9.6 x 10^-19 C

Answer 1

the options a,c,d are right

Answer 2

Answer: The correct answer is Option a, c and d.

Explanation:

Millikan’s oil drop experiment is used to measure the charge of an electron. Before this experiment, the subatomic particles were not accepted.

His apparatus contained an electric field that was created between the parallel pairs of metal plates that were held apart by using an insulating material. Electrically charged oil drops then entered the electric field and they were balanced between the two plates.

The charge on the oil drop was calculated using the equation:

$Q=\frac{m\cdot g}{E}$

He found that all the oil drops had charges that were the multiples of $1.6\times 10^{-19}C$. This value is the charge on 1 electron.

Number of electrons excess electrons is calculated by using the formula:

$\text{Excess electrons}=\frac{\text{Charge on millikan's oil drop}}{\text{Charge on 1 electron}}$

From the given options:

• Option a: $3.2\times 10^{-19}C$

$\text{Excess electrons}=\frac{3.2\times 10^{-19}}{1.6\times 10^{-19}}=2$

This can be taken as the charge on an oil drop.

• Option b: $8.3\times 10^{-19}C$

$\text{Excess electrons}=\frac{8.3\times 10^{-19}}{1.6\times 10^{-19}}=5.1875$

This cannot be taken as the charge on an oil drop.

• Option c: $4.8\times 10^{-19}C$

$\text{Excess electrons}=\frac{4.8\times 10^{-19}}{1.6\times 10^{-19}}=3$

This can be taken as the charge on an oil drop.

• Option d: $9.6\times 10^{-19}C$

$\text{Excess electrons}=\frac{9.6\times 10^{-19}}{1.6\times 10^{-19}}=6$

This can be taken as the charge on an oil drop.

Hence, the correct answer is Option a, c and d