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Faraday’s Ice Pail

Out of a humble ice pail the great experimentalist Michael Faraday created a device to demonstrate key principles of attraction, repulsion and electrostatic induction. 

Michael Faraday is considered by some historians as the greatest experimentalist in the history of science. It was largely due to his efforts that electricity became a viable technology.

Here we take a closer look at Faraday's ice pail, one of his many groundbreaking experiments exploring the nature of electricity.

This experiment illustrates the distribution of charge over a metal conductor and principles of electrostatic induction.

Instructions

  1. Note the metal sphere and metal pail. The sphere is charged with an electrostatic generator, giving it a net negative charge. The metal pail is electrically neutral, with evenly distributed negative and positive particles, as denoted in yellow and red.
  2. You can use the charge level slider to change the sphere’s charge from insignificant to low, medium, or high.
  3. Now click to lower the sphere into the pail using the sphere position slider. See how the negative charge on the surface of the sphere repels free electrons to the outside surface of the pail, and attracts positive particles to the inside surface of the pail.
  4. Observe the surplus of free electrons on the outside of the cup, flowing down a wire that connects to an electroscope, an early instrument for measuring electrical charge.
  5. With the sphere in the bucket, change the charge level to see how it displaces the electroscopes needle. The greater the charge, the farther the needle is displaced. This demonstrates that an induced charge (in the electrocsope) has the same magnitude as the inducing charge (in the metal sphere).