what is a transformer in electricity
In the field of electricity, a **transformer** is a device that utilizes the principle of **electromagnetic induction** to change the
alternating current (AC) voltage. Its core function is to **increase or decrease the voltage** while keeping the power (energy)
basically unchanged, and it is an essential component in power systems and electronic devices. I. The Core Principle of the Transformer The transformer operates based on the phenomenon of **mutual induction**: 1. An alternating current is connected to the **primary coil**, generating an alternating magnetic field. 2. The **iron core** guides the magnetic field to concentrate and pass through the **secondary coil**. 3. An alternating current of the same frequency is induced in the secondary coil, and the voltage is determined by the
**turns ratio**. II. Key Structures A transformer is mainly composed of three parts: 1. **Primary coil**: The input terminal connected to the power source. 2. **Secondary coil**: The coil that outputs the target voltage. 3. **Iron core**: Stacked by silicon steel sheets to enhance the magnetic coupling efficiency. III. The Relationship between Voltage and Current Voltage transformation is achieved through the turns ratio formula: IV. Main Classifications
| Classification Method | Type | Application Scenarios |
| By Purpose | Power transformer (high-voltage power transmission) | Substations, main lines of the power grid |
| Distribution transformer (step-down to 220V/380V) | Power supply for residential areas and factories | |
| Electronic transformer (low power) | Mobile phone chargers, power supplies for home appliances | |
| By the Number of Windings | Double-winding transformer | Common step-down/step-up transformers |
| Autotransformer (tapped single winding) | Motor starting, voltage regulators | |
| By Cooling Method | Oil-cooled transformer | High-power power transformers |
| Air-cooled transformer | Heat dissipation for electronic devices |
V. Practical Applications 1. **Power Transmission**: - Power plants step up the voltage (e.g., 10kV → 500kV) to reduce power transmission losses, and at the terminals,
the voltage is stepped down (e.g., 10kV → 220V) for household use. 2. **Electronic Devices**: - Mobile phone chargers (220V → 5V), welding machines (low voltage and high current). 3. **Industrial Equipment**: - Motor speed regulation, electric furnace heating, etc. VI. Efficiency and Losses - **Efficiency**: Usually as high as **90%–99%**, and the main losses are: - **Copper loss** (heating due to the resistance of the windings); - **Iron loss** (eddy current and hysteresis losses in the iron core). VII. Key Characteristics - **Only applicable to alternating current**: Direct current cannot generate an alternating magnetic field, so a transformer
cannot change the direct current voltage. - **Isolation function**: A double-winding transformer can isolate the primary and secondary circuits to ensure safety (such
as in medical devices). Conclusion The transformer is the "voltage bridge" of the power system. It efficiently realizes voltage conversion through electromagnetic
induction and is widely used in power generation, power transmission, power distribution, and electronic devices. Its core formula
**\(V_1/V_2 = N_1/N_2\)** is the key to understanding the principle of voltage transformation.
