Physics 2002 JAMB Past Questions - Question 44: From the generating station to each substation, power is transmitted at a very high voltage so as to reduce

Correct Answer

A

Explanation

Power is transmitted at a very high voltage from generating stations to substations in order to reduce energy losses during transmission. This process is a fundamental aspect of the electrical power distribution system, and it can be explained as follows:

1. **Generation**: Electricity is typically generated at power plants, which can use various energy sources such as coal, natural gas, nuclear, hydroelectric, or renewable sources like wind and solar. The electricity generated is in the form of alternating current (AC) at a relatively low voltage.

2. **Voltage Transformation**: Before electricity is transmitted over long distances, it goes through a transformer. This transformer increases the voltage significantly, typically to hundreds of thousands of volts. This high-voltage electricity is more efficient to transmit over long distances.

3. **Reducing Losses**: Ohm's law dictates that power loss in a transmission line is directly proportional to the square of the current and inversely proportional to the square of the voltage. In other words, for a given amount of power, increasing the voltage while reducing the current significantly reduces energy losses. This is described by the formula P = I²R, where P is power, I is current, and R is the resistance of the transmission line. By increasing the voltage, you can reduce the current and, consequently, the power losses.

4. **Transmission**: High-voltage electricity is then transmitted over long distances, often through a network of overhead power lines or underground cables.

5. **Step-Down Transformers**: As the electricity gets closer to its destination, it goes through step-down transformers at substations. These transformers reduce the voltage to a lower level, suitable for distribution.

6. **Distribution**: The lower-voltage electricity is then distributed through a network of power lines to homes, businesses, and other end-users.

By transmitting electricity at high voltage, energy losses are minimized, making the power distribution system more efficient. This is crucial for ensuring that a large portion of the electricity generated at power plants reaches its intended destination with minimal waste.