Which of these options are correct for a DC electric machine with a large air gap?

A DC electric machine with a large air gap typically aligns with certain characteristics in its operation and design. Among possible options regarding its performance and implications, here are the correct statements:

1. Increased Magnetizing Current: A larger air gap requires a higher magnetizing current to establish the same level of magnetic flux across the air gap compared to a smaller air gap. This is because air (or vacuum) presents a higher magnetic reluctance than the materials used in the machine core, necessitating more current to generate the required magnetic field strength.

2. Reduced Efficiency: The need for a higher magnetizing current leads to increased copper losses in the winding that carries this current. This, in conjunction with potential increases in other losses, can contribute to a reduction in overall machine efficiency.

3. Potential for Increased Physical Size: To accommodate the larger air gap while maintaining the necessary magnetic flux, the physical size of the magnetic circuit (core and yoke) may need to be increased. This is to ensure that the flux can be maintained at a level that allows the machine to operate effectively, despite the increased reluctance of the air gap.

4. Increased Leakage Flux: A larger air gap can result in an increase in leakage flux, which is the portion of the magnetic flux that does not follow the intended path in the magnetic circuit but instead leaks through surrounding space. This undermines the efficiency of magnetic field utilization in the machine.

5. Stability and Mechanical Tolerance Issues: While a larger air