Transformers

Formula to calculate either voltage or turns on one of the transformers

Vp ÷ Vs = Np ÷ Ns

Describe the use of the transformer in high-voltage transmission of electricity

When an electricity grid needs to supply electricity to many different places, a high current is needed; however this results in a lot of heat energy being lost. So the grid transmits electricity at a low current by increasing the voltage. Since a high voltage is dangerous to use in homes, transformers are used to step down this power supply, making it safe to use. So electricity is transmitted at high voltage and supplied to homes and buildings at low voltage.

Explain why power losses in cables are lower when the voltage is high

When the voltage is high, the resistance of windings and the formation of eddy currents is low, thus leading to lower power losses

Give advantages and disadvantages of high-voltage transmission

Advantages: - Lower power loss - Less resistance of windings - Less formation of eddy currents Disadvantages: - Dangerous to use in households

How is power calculated for transformers with 100% efficiency

Ip Vp = Is Vs

Describe the principle of operation of a transformer

The principle of operation of a transformer is by electromagnetic induction (the production of an electromotive force across an electrical conductor in a changing magnetic field)

Understand the terms step-up and step-down

A transformer can increase or decrease the voltage this way. When there are lesser turns on the secondary coil than the primary coil, the voltage produced in the secondary coil decreases. These are called step-down transformers. When the secondary coil has more turns than the primary coil, the voltage is 'stepped-up' so it is called a step-up transformer. The above is a step- down transformer as the no. of turns on the primary coil exceed the no. of turns on the secondary coil.

Describe the construction of a basic transformer with a soft iron core, as used for voltage transformations

A transformer is an electrical device that changes the voltage of an A.C. current supply. A transformer has two coils of wires wound around an iron core, a primary coil and a secondary coil, which are connected to the primary circuit and secondary circuit respectively. When an alternating current is applied to the primary coil through the primary circuit, an alternating voltage is induced in the secondary coil and thus an alternating current is induced in the secondary circuit. This happens due to electromagnetic induction.