MCQ Detailed View

The absolute charge of an electron was determined by Robert Millikan through his famous oil drop experiment in 1909. Millikan measured the tiny charge of individual oil droplets suspended in an electric field, allowing precise calculation of the electron’s fundamental charge, which is approximately 1.602 × 10⁻¹⁹ coulombs.

In the experiment, Millikan observed tiny oil droplets falling under gravity while applying an electric field to balance the gravitational force. By adjusting the field so that droplets were suspended in equilibrium, he could measure the force acting on the droplets. Using the known mass of the droplets and gravitational acceleration, he calculated the charge on each droplet. By analyzing multiple droplets, he discovered that all measured charges were multiples of a smallest value, which corresponds to the charge of a single electron.

Other scientists contributed to understanding the electron, but they did not determine its exact charge:

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  J.J. Thomson discovered the electron in 1897 and measured the charge-to-mass ratio (e/m) of the electron, not its absolute charge.

  
  


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  Chadwick discovered the neutron in 1932, which is neutral and unrelated to measuring electron charge.

  
  


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  Rutherford discovered the nucleus and described its structure, but did not measure the electron charge.

  
  

Millikan’s experiment was crucial in establishing the quantization of electric charge and validating early atomic models. Knowing the electron’s charge is fundamental in inorganic chemistry, electrochemistry, and physics, as it allows calculation of current, potential difference, stoichiometry in redox reactions, and behavior of ions.

In summary, the absolute value of the charge on an electron was determined by Robert Millikan, making his work a cornerstone in atomic theory and experimental physics.