Transformers And Their Principles of Operation - SS1 Physics Lesson Note

Transformers are electrical devices that are used to transfer electrical energy between two or more circuits through electromagnetic induction. They work based on the principles of mutual induction, where a changing current in one coil (known as the primary coil) induces a voltage in another coil (known as the secondary coil) that is in close proximity. Here are the key principles of operation of transformers:

1. Construction: A transformer consists of two or more coils of wire wound around a core made of a high-permeability material such as iron. The primary coil is connected to the input voltage source, while the secondary coil is connected to the load.

2. Mutual Induction: When an alternating current (AC) flows through the primary coil, it creates a changing magnetic field around the coil. This changing magnetic field induces an alternating voltage in the secondary coil according to Faraday's law of electromagnetic induction.

3. Turns Ratio: The ratio of the number of turns in the primary coil (N1) to the number of turns in the secondary coil (N2) is known as the turn ratio. It determines the voltage transformation ratio of the transformer. The turns ratio is given by N1/N2, and it determines whether the transformer steps up or steps down the voltage.

4. Voltage and Current Transformation: In an ideal transformer (assuming no losses), the voltage across the primary coil (V1) is proportional to the voltage across the secondary coil (V2) based on the turn ratio. If the turns ratio is greater than 1 (N1 > N2), the transformer is a step-up transformer and V2 > V1. If the turns ratio is less than 1 (N1 < N2), the transformer is a step-down transformer and V2 < V1. However, the current in the primary and secondary coils is inversely proportional to the turns ratio, according to the principle of conservation of energy.

5. Power Transformation: A transformer can also transform the power between the primary and secondary coils. Power is given by the product of voltage and current. If the voltage is stepped up, the current is stepped down to maintain the power balance, and vice versa. The power output is ideally equal to the power input, neglecting losses.

6. Efficiency and Losses: Transformers are not perfectly efficient, and energy losses occur due to resistive losses in the windings and core losses due to hysteresis and eddy currents. These losses result in a decrease in the overall efficiency of the transformer.

Transformers are widely used in electrical power systems to step up or step down voltage levels for the transmission and distribution of electrical energy. They are also used in electronic devices, such as power supplies and audio amplifiers, to provide appropriate voltage levels. The principles of operation of transformers make them essential components in the efficient and reliable transfer of electrical energy.