Transformers are special devices that work with alternating current (AC). They use a process called electromagnetic induction to transfer energy. Here are the main parts of how they work:

1. Electromagnetic Induction: When AC runs through the primary coil, it creates a magnetic field that changes over time. This changing magnetic field makes a voltage in the secondary coil, allowing the energy to move from one coil to another.

2. Turn Ratio: The amount of voltage a transformer creates depends on what we call the turn ratio. This is the number of turns (or loops) in the coils. It’s calculated like this:

   • The turn ratio, ( n ), is:
   $$n = \frac{N_p}{N_s}$$
   • Here, ( N_p ) is the number of turns in the primary coil, and ( N_s ) is the number of turns in the secondary coil. The relationship between the primary voltage (( V_p )) and the secondary voltage (( V_s )) can be shown as:
   $$\frac{V_p}{V_s} = \frac{N_p}{N_s}$$

3. Efficiency: Transformers are really good at what they do. They can be more than 95% efficient, which means they lose very little energy as heat or through magnetic problems.

4. Applications: You’ll find transformers in power systems. They help increase high voltages for transmission. This is important because higher voltages, like 400 kV, reduce the current. Less current means less energy loss over long distances.

5. Unique Characteristics:

   • Core Material: Transformers are made from laminated silicon steel. This special material helps reduce energy loss.
   • Phase Relationship: The design of a transformer can change the phase when needed, which is important for AC systems.

These features make transformers very important in AC circuits. They don’t work well with direct current (DC) circuits because there’s no changing magnetic field.