Unlike a child's hair reacting to a balloon, where each strand is repelled from the others by static electricity (i.e. not flowing in a current, but charged), an electric current can consist of any moving charged particles.
Most commonly, these charged particles are are electrons.
But any charge in motion constitutes a current. And, in moving, it has the capacity to do Work.
In 1831, Michael Faraday discovered that the movement of a magnet through a coil of copper wire induces the flow of electricity through a circuit. This is called electromagnetic induction.
With this discovery, Faraday provided the technology to build the modern world.
And now, in 2015, the capacity to store electrical energy efficiently is about to trigger a revolution almost as big.
Even today, 180 years after Faraday discovered electromagnetic induction, almost every time an electrical appliance is used, there is an electrical generator running somewhere to provide the flow of electrons. And, in order to provide this electrical energy, it has to be converted from chemical energy.
It seems astonishing that the process of providing electrical energy to modern societies still relies largely on the combustion of fossil hydrocarbons such as coal and petroleum.
Even more surprising is that the heat generated from the combustion must first be used to heat water, before the production of steam can cause turbines to turn one of Faraday's electrical generators.
So, energy conversion, capture and storage has become the most significant unsolved problem of our time.
There are several technologies which are able to store the energy from Work for conversion to electricity when the demand arises. Some are widely used, such as the flow of water under gravity (hydroelectric), others are experimental, such as flywheel storage.
However, at the present, there is a convergence of pressure from several forces to implement an economic, affordable, environmentally-acceptable system for the storage of energy.
And, because of both the pragmatism and the entrepreneurial courage of some individuals such as Elon Musk, the developed world may be about to witness a technological revolution. Tesla Motors plans to build the world's largest Lithium-ion battery factory, called the Gigafactory, before 2020. The factory would be approximately 10,000,000 square feet (930,000 m2) in size and will produce 35 gigawatt hours of cells per year.
The company, Tesla, is named in homage to the genius showman inventor Nicola Tesla (1856 - 1943) from Serbia.
The SI unit of magnetic flux density, the tesla, was named after him.
Lithium-ion batteries are rechargeable because they involve the movement of lithium ions back and forth between two electrodes depending upon whether there is a discharge of electricity or a charging from an external source such as a photovoltaic cell.
They have a high energy density storage capacity and no memory effect and they are light.
Because they usually contain a flammable electrolyte and are kept pressurized, they can be dangerous.
Look for one to appear on the wall of a house near you in the near future!