1. What Is a Transformer?
A transformer is an electrical device that changes the voltage of an alternating current (AC). It can either increase (step-up) or decrease (step-down) the voltage, depending on how it’s designed.
2. Main Parts of a Transformer
Primary coil: The input side, where AC current enters.
Secondary coil: The output side, where the transformed voltage comes out.
Core: Usually made of iron, this links the magnetic field from the primary to the secondary coil.
The coils are not physically connected—everything happens through magnetism.
3. AC Current Enters the Primary Coil
When an alternating current flows into the primary coil, it constantly changes direction. This creates a changing magnetic field around the coil.
4. Magnetic Field Travels Through the Core
This magnetic field doesn’t just stay in the air—it travels through the iron core, which guides and strengthens the field. The field then reaches the secondary coil.
5. Voltage is Induced in the Secondary Coil
Because the magnetic field is changing, it causes a voltage to appear in the secondary coil. This process is called electromagnetic induction. No electricity is directly passed between the coils—only the magnetic field does the work.
6. The Voltage Changes
Whether the voltage goes up or down depends on how many loops (called turns) are in each coil:
More turns in the secondary coil = higher voltage (step-up transformer).
Fewer turns in the secondary coil = lower voltage (step-down transformer).
The design of the coils decides what the transformer does.
7. Electricity Comes Out Changed
Now the secondary coil has its own AC voltage, either increased or decreased from the original. This output goes to the devices or systems that need it.
8. Energy Efficiency
Transformers are usually very efficient. In ideal conditions, almost no energy is lost. However, small losses can happen due to heat, resistance in the wires, or slight imperfections in the core.