The smallest unit of charge is - 1.6*10-19 C, which is the charge in coulombs of a single electron. Robert Millikan was able to measure the charge on small droplets of oil by suspending them between a pair of electrically charged plates. Which of the values are possible charges of those oil droplets?

The possible charges of those oil droplets from the given choices are:

Option B: - 3.2 * 10⁻¹⁹ C

Option C. - 4.8 * 10⁻¹⁹ C

Option E. - 8 * 10⁻¹⁹ C

Explanation:

Since the minimum amount of charge is - 1.6 * 10⁻¹⁹ C, the charge of any matter must be a multiple of that number.

So, find which of the given choices is a multiple of - 1.6 * 10⁻¹⁹ C.

You do that by dividing each choice by - 1.6 * 10⁻¹⁹ C. If the division is a whole number (zero remainder) then the choice is a multiple of - 1.6 * 10⁻¹⁹ C and is a possible charge of the oil droplets:

Since all the powers are 10⁻¹⁹ you must only divive the mantissas:

Option A. - 1.2 * 10⁻¹⁹ C

1.2 / 1.6 = 0.75. Not an integer number, so this is not a possible charge.

Option B: - 3.2 * 10⁻¹⁹ C

3.2 / 1.6 = 2. Therefore this is a possible charge of the oil droplets.

Option C. - 4.8 * 10⁻¹⁹ C

4.8 / 1.6 = 3. Hence, this is also a possible charge of the oild droplets.

Option D. - 5.6 * 10⁻¹⁹ C

5.6 / 1.6 = 3.5. So, this is not a possible charge.

Option E. - 8 * 10⁻¹⁹ C

8 / 1.6 = 5. Therefore, this is a possible charge.

Option F. - 9.4 * 10⁻¹⁹ C

9.4 / 1.6 = 5.875. Hence, this is not a possible charge.