Step-up transformers are essential because they allow power generation at what range?

Step-up transformers are crucial components in electrical power generation and transmission systems because they increase voltage levels to enhance the efficiency of power transfer over long distances. The essential role of a step-up transformer is to elevate the voltage from the generator's output to a level that is optimal for transmission.

When power generation occurs in the range between 10 kV and 25 kV, the use of a step-up transformer becomes particularly beneficial. This range is significant because it enables the electrical energy to be transmitted more efficiently, reducing energy losses due to resistance in transmission lines. By stepping up the voltage, the current is reduced for the same power level, which results in lower heat losses and better efficiency in conveying electricity across substantial distances.

Operating above this range allows power to be distributed more effectively, ensuring that it can reach residential and industrial consumers without substantial energy loss. In contrast, voltages below 10 kV are generally insufficient for long-distance transmission, while options suggesting voltages above 25 kV or 35 kV indicate levels where step-up transformers continue to play an important role but do not directly address the optimal operational range specified in the question.