Sources of electric current

Electrical equipments will function when there is electrical energy. The electric current from electrical energy source flow through the electrical equipment. Thus, the flow of this electric current is utilized by electrical equipment. 

The source of an electric current must have a potential difference in order to generate the electric current.

Batteries are not the only source of electric current. There are many other sources of electric current.

Sources of electric current are often referred to as electrical elements or electrical cells. Electrical elements can be divided into two types, namely the primary and secondary elements.

The primary element is the element that can not be used again if it runs out. Secondary elements can be used repeatedly, or rechargeable.

The Voltaic cell or Galvanic cell was discovered by Alessandro Volta in 1800.

The voltaic cell has 3 important components:
  • Positive pole (anode) made of copper (Cu);
  • Negative pole (cathode) made of zinc (Zn);
  • An electrolyte solution, which is a solution of sulfuric acid (H₂SO₄).

The voltaic cell is able to produce electrical voltage of 1.1 volt, but it does not endure for a long time, because the reaction at the positive pole produce hydrogen gas and it is blocking the electric current, so the voltaic cell can not be used for a long time.
In addition, the voltaic cell is not practical, because it requires a liquid solution of sulfuric acid. Thus, voltaic cell is not a portable cell.

Dry element was first discovered by Leclanche. The dry element is very practical, because it has a dry electrolyte solution. In addition, the dry element can generate electric currents longer than the voltaic cell.

In general, the dry element (battery) consists of:
  • Positive pole or anode made of carbon rod (C).
  • Negative pole or cathode made from zinc (Zn).
  • Electrolyte solution made from ammonium chloride. (NH₄Cl).
  • Depolariser made of manganese dioxide (MnO₂).

An accumulator is a secondary wet element. That is, after it is used, the accumulator can be recharged and can be reused.

The accumulator cell consists of 3 parts, namely:
   • Anode of lead dioxide (PbO₂);
   • Cathodes of pure lead (Pb);
   • Electrolyte solution of sulfuric acid with a concentration of 30%.

A potential difference of 1 accumulator cell is 2 volts. In daily life, we often find the 12 volts of accumulator to ignite the car's engine, which consist of 6 cells of accumulator.