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How Do Electrical Transformers Work

What is a transformer?

When you are out and about in the car and spot all those immense power lines painting the skyline across country and through our cities carrying electricity at very high voltage to our homes and places of work they are often rated at between 400,000 and 700,000 volts. Considering that our home appliances are typically rated at a mere 110 to 240 volts then you understand that there must be some way of reducing the high voltage electricity delivered between the power lines and our homes and places of work. The name for the bit of kit that does this, buzzing with electromagnetic energy as it works is a ‘transformer.’

Electrical induction

In order to get a grasp of how electrical transformers work you need to first understand the principle of electrical induction. Faraday hypothesized that if magnetism can be produced by electricity then the reverse is also true. He tested this and the conclusion was that although a steady magnetic field was unable to produce electric current, a change in magnetic field could. This is called an induced current and the process is known as electromagnetic induction.

The electrical transformer introduced

The electrical transformer is any device that serves to increase or decrease the voltage of alternating current. It functions as the current in one coil induces current in another. Inside a transformer there are two coils (primary and secondary) which are wrapped around a metal core.

The transformer works when an alternating current is passed through the primary coil and a magnetic field (induced electromagnetic induction) makes a current flow into the secondary coil. Depending on the number of loops of wire in the primary compared to the secondary coil, you will have a step up or step down transformer. Explained below…

The number of loops in the secondary coil are greater than in the primary coil = greater voltage in the secondary coil = a step up transformer

The number of loops in the secondary coil are fewer than in the primary coil = less voltage in the secondary coil = a step down transformer

As previously mentioned there are some truly enormous transformers that hum away in our towns and big cities that serve to convert electricity from power lines into lower voltages. Of course this is an obvious example of step down transformers. But on a more micro scale, there are also lots of transformers inside our homes.

While bigger white goods like dishwashers and washing machines use 110-240 volts (relatively high for in the home), other electronic devices that we use like tablets, mobile phone chargers etc. use very small voltages (6-15v) and as such they have small transformers built into their power leads to convert the 110-240 volts of domestically supplied electricity into a tiny voltage that will not cause them damage, probably by explosion! So step down transformers really are a big part of our daily lives, even if more often than not we don’t notice them!