Physics Lab Equipment

LEAI-42 Apparatus of Millikan's Experiment - Advanced Model

LEAI-42 Apparatus of Millikan's Experiment - Advanced Model


  • CCD acquisition and LCD display to eliminate eye fatigue

  • Electronic graduation scales on screen

  • Voltage, time and oil image displayed on one screen

  • Optional Brownian motion experiment with 120X objective


This LEAI-42 apparatus of Millikan's oil drop experiment is the advanced version of the series with CCD image acquisition and monitor display. It is designed to verify the quantum nature of electrical charges, measure the elementary charge of an electron, observe the Brownian motion of oil drops, and verify the normal distribution of the displacement probability of oil drops. Unlike the conventional setup with an eyepiece and a stopwatch, this setup displays voltage, time, and oil drop image simultaneously so that the experiment can be conducted more accurately without eye fatigue.

The instruction manual contains comprehensive materials including experimental configurations, principles and step-by-step instructions. Please click Experiment Theory and Contents to find more information about this apparatus.


This apparatus possesses the following advantages:


1. Electronic graduation scales are stable, not affected by the distortion of the display.

2. Image of oil drops is clear and bright with a high contrast.

3. Better observation of Brown movement with a 120X TV microscope.

4. Graduation scale, voltage, time, and oil drop image displayed on one screen.

5. Output signal compatible with various display devices such as TV, projector, recorder and so on.


Using this apparatus, the following experiments can be conducted:


1. Verify the existence of positive and negative electrical charges

2. Verify the quantum nature of electrical charges

3. Measure the elementary charge of an electron

4. Observe and measure Brownian motion (optional)

5. Verify normal distribution of displacement probability (optional)


Operating voltage between upper and lower platesDC ± 0 ~ 700 V, adjustable, 3-1/2 digit, resolution 1 V
Elevation voltage200 ~ 300 V
Distance between upper and lower plates5 ± 0.01 mm
Magnification of objective lens60X and 120X
Electric timer0 ~ 99.99 s, resolution 0.01 s

Electronic graduation of scale

Type A: 8×3 grid, 0.25 mm/div with 60X objective
Type B: 15×15 grid, 0.08 mm/div with 60X objective

& 0.04 mm/div with 120X objective

Parts List

Main unit1
Oil sprayer1
Bottle of oil (15 mL)1
LCD monitor (9-inch)1
120X objective lens1
Power cord1

      Apparatus of Millikan's Experiment.png

Schematic diagram of oil drop chamber

1 oil mist cup, 2 oil shutter, 3 windscreen, 4 upper electrode, 5 oil drop channel, 

6 lower electrode, 7 base stand, 

8 cover, 9 oil spray aperture, 

10 oil mist aperture, 11 electrode clamp, 12 oil channel base

      Apparatus of Millikan's Experiment.png

Schematic of upper panel of main unit

(Click figure to enlarge)

      Apparatus of Millikan's Experiment.png

Quantity of elementary charge vs total charges carried by various oil drops

(Click figure to enlarge)

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