GCSE Physics Tutorial: Transformer Ratio and Coil Turns

Transformers are fundamental devices in the field of electricity, allowing us to change the voltage levels of alternating current (AC) to suit different applications. One of the key aspects that determine the transformation of voltage is the ratio of the number of coils on the primary and secondary sides of the transformer. In this tutorial, we will explain how the ratio of potential difference is dependent on the number of coils on each side of a transformer.

Coil Turns and Transformer Ratio

A transformer consists of two coils, the primary coil and the secondary coil, wound around a common iron core. The primary coil is connected to the input voltage source, while the secondary coil is connected to the output circuit. The number of turns of wire in each coil plays a crucial role in determining the transformation ratio of the transformer.

The transformation ratio, often denoted as n, is defined as the ratio of the number of turns in the secondary coil (N₂) to the number of turns in the primary coil (N₁):

n = N₂ / N₁

Voltage Transformation

The transformation ratio directly affects the voltage transformation of the transformer. When the primary coil is connected to an alternating current (AC) source, it creates a changing magnetic field. This changing magnetic field induces a voltage in the secondary coil through electromagnetic induction.

The induced voltage in the secondary coil (V₂) is proportional to the ratio of the number of turns in the secondary coil to the number of turns in the primary coil:

V₂ / V₁ = N₂ / N₁ = n

Where:

• V₁: Voltage across the primary coil

• V₂: Voltage across the secondary coil

This means that if the secondary coil has more turns than the primary coil (n > 1), the output voltage will be higher than the input voltage. Conversely, if the secondary coil has fewer turns than the primary coil (n < 1), the output voltage will be lower than the input voltage.

Current and Power Transformation

It's important to note that while the voltage changes with the transformer ratio, the current and power also change inversely. If the voltage increases, the current decreases to maintain the conservation of energy.

Additionally, in an ideal transformer (neglecting losses), the power on the primary side is equal to the power on the secondary side:

P₁ = P₂

This power equality is a fundamental principle of transformers and is based on the conservation of energy.

Conclusion

The ratio of potential difference in a transformer is dependent on the number of coils on each side. The transformation ratio, represented by n, is the ratio of the number of turns in the secondary coil to the number of turns in the primary coil. This ratio determines how the voltage is transformed in the transformer, leading to higher or lower output voltage compared to the input voltage, while keeping the power conserved.

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