Michael Faraday's voltammeter

The way we quantify electricity was first devised by Michael Faraday using this piece of apparatus, known as a voltammeter.

  • Credit: Paul Wilkinson
  • Date

    1833
  • Place made

    Basement laboratory at the Ri

  • Alternative name

    Volt-electrometer
  • People

  • Materials

    Glass, metal

  • Measurements

    H: 261mm, W: 182mm, D: 117mm

  • Key words

    Michael Faraday, experiment, electricity

Description

The way we quantify electricity was first devised by Michael Faraday using this piece of apparatus, known as a voltammeter. It worked by measuring the amount of gas evolved when electricity was passed through chemical compounds to decompose them into their individual elements. Faraday used it to formulate his laws of electrolysis, including the law that the same quantity of electricity, no matter what its source, decomposes the same quantity of matter.

Faraday had been researching electricity in the early 1820s, and made some key discoveries, such as the electric motor. However, he was later directed onto other projects by Humphry Davy, and it wasn’t until after Davy’s death in 1829 that Faraday could continue his work on electricity.

He made several important findings in quick succession, first discovering electro-magnetic induction and then inventing both the electric transformer and generator in 1831. The following year he began to concentrate on electro-chemistry. Davy may have considered this subject to be his territory, which is why Faraday took so long to start investigating it, but when he did he found that he had to correct several of Davy’s theories. For example, he discovered that electro-chemical action took place not at the poles, as Davy had stated, but in the solution undergoing decomposition. This discovery was important for understanding the nature of electricity.

Faraday also introduced the terms we use today in electrochemistry: what Davy referred to as poles, Faraday called ‘electrodes’. Faraday divided electrodes into ‘anodes’ and ‘cathodes’, with ‘ions’ passing between them.

More images

  • Michael Faraday's voltammeter

    Michael Faraday's voltammeter - full view

    Credit: Paul Wilkinson

  • Michael Faraday's voltammeter

    Michael Faraday's voltammeter - detail

    Credit: Paul Wilkinson

Where can I view this?

The voltammeter is on display in the Faraday Museum, opposite the elements game.

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