What is a step-down transformer and how does it change voltage levels?

The operation of a step-down transformer is based on the principles of electromagnetic induction. When an AC current flows through the primary winding, it creates an alternating magnetic field around it. This magnetic field then induces a voltage in the secondary winding through mutual induction. The magnitude of the induced voltage depends on the ratio of the number of turns in the primary and secondary windings.

The voltage transformation ratio (or turns ratio) of a transformer is given by:

Voltage ratio = Np / Ns

where Np is the number of turns in the primary winding and Ns is the number of turns in the secondary winding.

Since the primary winding has more turns than the secondary winding in a step-down transformer (Np > Ns), the voltage ratio is greater than 1. This means that the output voltage (Vout) will be lower than the input voltage (Vin) according to the following equation:

Vout = Vin / Voltage ratio

So, a step-down transformer reduces the voltage level at the output, making it suitable for applications where lower voltage is required, such as in household electrical systems, electronic devices, and many industrial applications.

It's important to note that while the voltage is decreased in a step-down transformer, the current is proportionally increased to satisfy the law of conservation of energy. In an ideal transformer (without losses), the power on the input side is equal to the power on the output side, neglecting small losses due to resistance, magnetization, and core losses.