Millikan's Oil Drop Experiment showed that the elementary charge is the smallest unit of charge; this supports:

Millikan's Oil Drop Experiment showed that the elementary charge is the smallest unit of charge; this supports:

• A. Measured the elementary charge as the smallest unit of charge, supporting charge quantization
• B. Invented the capacitor
• C. Measured resistance of air
• D. Discovered electron orbit

Answer: (A)

The main idea is that electric charge comes in discrete units, rather than being continuous. Millikan’s oil drop experiment determined the elementary charge e by balancing the gravitational force on tiny charged oil droplets with the electric force from an applied field. By adjusting the field to hold droplets at rest, the charge on each droplet could be measured. The observed charges were always integer multiples of the same smallest value, indicating that charge is quantized and that e is the smallest unit of charge. This is why the correct option is the best one: it directly states that the experiment measured the elementary charge as the smallest unit of charge, supporting the idea of charge quantization. The other options don’t fit because they describe different discoveries or devices (inventing a capacitor; measuring air resistance; discovering electron orbit) that Millikan’s work did not establish.

The main idea is that electric charge comes in discrete units, rather than being continuous. Millikan’s oil drop experiment determined the elementary charge e by balancing the gravitational force on tiny charged oil droplets with the electric force from an applied field. By adjusting the field to hold droplets at rest, the charge on each droplet could be measured. The observed charges were always integer multiples of the same smallest value, indicating that charge is quantized and that e is the smallest unit of charge.

This is why the correct option is the best one: it directly states that the experiment measured the elementary charge as the smallest unit of charge, supporting the idea of charge quantization.

The other options don’t fit because they describe different discoveries or devices (inventing a capacitor; measuring air resistance; discovering electron orbit) that Millikan’s work did not establish.