What is Electricity?

Most of us take Electricity for granted, but without it life would be very different.

Have you ever wondered how all your everyday Electrical items work, from light bulbs to computers, and all those useful items that work off batteries, like TV remotes, and your mobile phone.

Electricity powers your devices from stored Electrical energy stored in a battery or supplied to your homes from an Energy Supplier.

Generally there are two types of Electricity we use, with the first being DC (Direct Current), as used in Batteries. Direct Current refers to the flow of electrons, from the battery to the device being powered (For example a torch bulb or a fan motor), and back to the battery. The drawing below shows the comparison between Electrical current flow, and water flowing from a water tank to a water wheel.

The power (Measured in Watts “W”) from the Battery is determined by Electrical pressure (Measured in Volts “V”) pushing the electrons around the circuit, and the flow rate (Measured in Amps “I”).

Power = Volts x Amps (W=VxI).

Comparing with water, the Battery Voltage is similar and proportional to the height of the water, as the higher the water tank is, then the greater the water pressure would be.

Water pressure to our houses is maintained at a steady pressure by being stored in large water tanks like below.

Comparing the water pressure (dependent on the height of the water), to Electrical pressure, the Voltage of the Battery determines this. Common batteries like the AA batteries found in torches are 1.5 Volts, where as Car batteries, needing greater power, are 12 volts.

The flow of the water is not only dependent on the pressure, but also on size of the pipes and how much the tap is turned on, (for example having a very long garden hose will drop the water pressure coming out the end). Likewise the flow of electrical current is dependent on the size and length of electrical wires (Bigger diameter cables can carry more electrical current), and the resistance of the load (Larger the electric motor or Electric light bulb, the greater the electrical flow, for example).

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The other type of Electricity is AC (Alternating Current). This is used for supplying Electrical Energy to our houses, offices and factories. With AC the Voltage (Electrical Pressure) goes up and down, cycling at 50 to 60 time a second. With AC electricity it is a lot simpler for the Electricity supplier to Generate higher voltages (Higher electrical pressures), so as it can be transported across the country easily, then dropped down in voltage using a transformer to enter our homes.

This drawing is a simplified version of AC Electrical power distribution, as generally different Voltages are used at different parts of the Power network which also differs from one country to the next.

Many different ways are used to generate electricity, around the world, from Coal powered power stations, to greener energy, like Solar and Wind.

The power generated is fed to a National Grid, so it can shared around the country, and added to by multiple other Power Stations.

In towns and cities we don’t see how the Electricity is brought to our homes, offices and factories as it is carried by underground cables, but the vast majority of this Electricity, is transported from the power stations to us by overhead cables, supported on pylons.

The reason for transporting Electricity over large distances (for example from one side of the county to the other), at High Voltages, is to avoid losses. Remember like water at high pressure (from a high water tank) will drop in pressure over a long distance of water pipe. A substation is used by the Energy Supplier to transform this High voltage down to more lower voltage for distribution to towns and Cities, usually underground.

Overhead cables are sometimes used in the countryside to transport the Electricity from the Substations, to rural areas, where it will be Transformed down again to the lower Voltages used in homes (110V to 250V).

AC Electricity can be compared to water travelling across the sea, in waves, with the higher the height between the crests and the troughs of water being similar to the greater the Voltage between peaks and and dips of an Electrical wave. Plus the speed of flow of the water waves can be compared to the Electrical flow measured in Amps. As the Power supplied is equal to the Voltage X Amps, it can also be seen that a High Wave of water flowing fast across the sea will have a lot more Energy than a much smaller wave travelling at a slower speed.

Compare the power from the wave above to the wave below!

Although we can not see Electrical waves; from the different water waves above we can appreciate why we need higher Voltage Electrical Energy to transport Electricity over large distances, from the power stations to our homes offices and factories.