GCSE Physics Tutorial: Step-up and Step-down Transformers in Electrical Power Transmission

Transformers play a crucial role in the efficient transmission and distribution of electricity in the National Grid. Step-up transformers are used to increase the potential difference (voltage) from power stations to transmission cables, while step-down transformers are used to decrease the voltage to a much lower value for domestic and industrial use. In this tutorial, we will recall the functions of step-up and step-down transformers and their significance in electrical power transmission.

1. Step-up Transformers: Step-up transformers are located at power stations, where electricity is generated. Their primary function is to increase the potential difference (voltage) of the electricity before it is transmitted through the National Grid. The voltage is increased to very high levels (typically hundreds of kilovolts) to minimise energy losses during long-distance transmission.

2. Step-up Transformation Process: The step-up transformation process involves two coils of wire wound around a laminated iron core. The coil with more turns, known as the secondary coil, is connected to the transmission lines, while the coil with fewer turns, known as the primary coil, is connected to the generator producing electricity.

3. Voltage Ratio: The voltage ratio of a step-up transformer is greater than one. The primary voltage (V_primary) and the secondary voltage (V_secondary) are related by the equation:

V_secondary = V_primary × (Number of turns in secondary coil / Number of turns in primary coil)

4. Significance of Step-up Transformers: Step-up transformers are essential in the National Grid for the following reasons:

• They enable efficient long-distance transmission of electricity with reduced energy losses, as higher voltages result in lower current flow.

• High-voltage transmission lines can carry large amounts of electrical power, making it feasible to transport electricity from power stations to substations across considerable distances.

5. Step-down Transformers: Step-down transformers are positioned at substations in the National Grid. Their primary function is to decrease the potential difference (voltage) of the electricity before distributing it to consumers for domestic and industrial use. The voltage is reduced to safe and practical levels for electrical devices and appliances.

6. Step-down Transformation Process: The step-down transformation process also involves two coils of wire wound around a laminated iron core. However, in step-down transformers, the secondary coil has fewer turns, and the primary coil has more turns.

7. Voltage Ratio: The voltage ratio of a step-down transformer is less than one. The primary voltage (V_primary) and the secondary voltage (V_secondary) are related by the equation:

V_secondary = V_primary × (Number of turns in secondary coil / Number of turns in primary coil)

8. Significance of Step-down Transformers: Step-down transformers are essential for distributing electricity to consumers:

• They reduce the voltage to safe levels suitable for domestic and industrial use.

• The lower voltage at this stage ensures the safety of electrical devices and appliances and prevents electrical hazards.

9. Summary: Step-up transformers increase the voltage of electricity from power stations to transmission cables, enabling efficient long-distance transmission with reduced energy losses. On the other hand, step-down transformers decrease the voltage to safe and practical levels for distribution to consumers. Together, these transformers play a crucial role in the National Grid, ensuring the smooth and reliable transmission and distribution of electricity to meet the energy needs of households, businesses, and industries.

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