Transformers are essential in the National Grid for increasing and decreasing the potential difference as needed. Transformers consist of two coils: the primary coil and the secondary coil, both of which are wrapped around an iron core.

If the transformer increases the potential difference, the secondary coil has more turns than the primary coil. This type of transformer is called a step-up transformer and is used to increase the potential difference for electricity transportation via cables. If the transformer decreases the potential difference, the secondary coil has fewer turns than the primary coil. This is known as a step-down transformer and is used to reduce the potential difference before electricity reaches homes.

Transformers are nearly 100% efficient.

Because transformers are nearly 100% efficient, almost no power $(P=VI)$ is lost when energy moves across a transformer and so we can write:

• $V2$= the potential difference in the secondary coil in volts (V)
• $I2$= the current in the secondary coil in amps (A)
• $V1$= the potential difference in the primary coil in volts (V)
• $I1$= the current in the primary coil in amps (A)

Formula