Question

In a Millikan oil-drop experiment, the charges on several different oil drops were as follows: -5.92; -4.44; -2.96; -8.88. The units are arbitrary. What is the likely value of the electronic charge in these arbitrary units?

	a.	-1.11
	b.	-1.48
	c.	-2.22
	d.	-2.96
	e.	-5.55

Answer 1

The values of charges for different oil drops must be integral multiple of electronic charge.

Hence, the values, -5.92, -4.44, -2.96 and -8.88 must be an integral multiple of our answer. This is because of quantisation of electronic charge in terms of charge of an electron.

Hence, lets check if the given options satisfies the above condition.

The values -5.92 and -2.96 are not integral multiple of -1.11.

Hence, -1.11 can nnot be our answer for electronic charge.

Note that all the value of charges are in fact integral multiples of -1.48.

Hence, -1.48 is an acceptable and likely value of electronic charge in the arbitrary unit.

-2.96 and -5.92 can not be written as integral multiple of -2.22. Hence, it can not be our answer.

While the values of charges, -5.92, -8.88 and -2.96 are integral multiple of -2.96, the value -4.44 is not an integral multiple.

Hence, it also can not be our answer.

Clearly, none of the values of charges are integral multiple of -5.55. Hence, this is also not our answer.

Hence, he correct choice is b. -1.48.