Electrical cells and cirrcuits
Cells are chemical systems
A cell is a chemical system in which certain chemical reactions cause the flow of electricity (flow of electrical charge) which is brought about by means of an external circuit. A cell is a source of electrical energy. An electrical cell consists of two solid electrodes that are made from different materials in an electrolyte.
Electrodes
Electrodes are made form different metals, the one serves as a positive terminal (pole) and the other one as the negative terminal (pole) of the cell.
Electrolyte
The electrolyte is a solution that can conduct electricity and consists of thousands of positive and negative particles that we call ions. When the two electrodes are connected in a circuit, a chemical reaction takes place in the cell. The chemical reactions cause the flow of electrical charge (electrons) through an external circuit.
A cell is a source of electricity
The chemical material in a cell contains stored or chemical potential energy, chemical energy is converted to electrical energy and then to kinetic energy where the chargess move through the external circuit. In ther words, a cell provides the power to sendd a current through a circuit. The power is called voltage and is measured in volts (V). Which measure the amount of energy that the cell provides to each charge (of electrons).
Flow of electricity
Electricity in a cell will always flow from an area that is more negatively charged (area with excess electrons) to an area that is more positively charged (has a shortage of electrons. We call this difference in charge between the terminals of a cell the potential difference or voltage. There has to be a potential difference in an electric circuit for electricity to flow. After a while the chemical enery in the cell will be depleted since the chemicals in the cells would have been use up. We say that the cell is flat.
Dry and wet cells
The cells in toys, radios and torches are called dry cells. A car battery is a wet cell and although it looks different to dry cells, all cells operate according to the same principles to covert chemical energy to electrical energy. When metals are squeezed into a lemon, the acid in the lemon is suitable liquid (electrolyte) for the manufacture of a cell. This cell cannot generate sufficient current to cause a light bulb to emit light, but can cause a LED (light emission diode) to emit light.
A battery
When two or more cells are connected, it is called a battery. In series (positive to negative)- the voltage is added together, and produces more energy to the charges that move through the circuit. In parallel (positive to positive and negative to negative) the voltage is the same as for one cell, but each one should only generate one third of the current-thus the cells will last longer.