Electricity and Magnetism

Essential ideas:

• When charges move an electric current is created.
• One of the earliest uses for electricity was to produce light and heat. This technology continues to have a major impact on the lives of people around the world.
• Electric cells allow us to store energy in a chemical form.
• The effect scientists call magnetism arises when one charge moves in the vicinity of another moving charge.

Electrical theory demonstrates the scientific thought involved in the development of a microscopic model (behaviour of charge carriers) from macroscopic observation. The historical development and refinement of these scientific ideas when the microscopic properties were unknown and unobservable is testament to the deep thinking shown by the scientists of the time.

Although Ohm and Barlow published their findings on the nature of electric current around the same time, little credence was given to Ohm. Barlow’s incorrect law was not initially criticized or investigated further. This is a reflection of the nature of academia of the time with physics in Germany being largely non-mathematical and Barlow held in high respect in England. It indicates the need for the publication and peer review of research findings in recognized scientific journals.

Scientists need to balance the research into electric cells that can store energy with greater energy density to provide longer device lifetimes with the long-term risks associated with the disposal of the chemicals involved when batteries are discarded.

Magnetic field lines provide a powerful visualization of a magnetic field. Historically, the field lines helped scientists and engineers to understand a link that begins with the influence of one moving charge on another and leads onto relativity.