**The Placement of Brushes in Electrical Machines**

The placement of brushes in electrical machines, such as generators and motors, is crucial for their proper functioning. The brushes are responsible for making electrical contact with the rotating part of the machine, known as the commutator or slip rings, which allows the transfer of current between the stationary and rotating parts.

There are two important axes associated with electrical machines: the magnetic neutral axis and the geometrical neutral axis. The magnetic neutral axis is the axis along which there is no magnetic field, while the geometrical neutral axis is the axis along which there is no mechanical displacement.

**Explanation of the Correct Answer: Option A**

The correct answer to the question is option A, which states that the brushes are placed along the magnetic neutral axis. This placement is necessary to ensure efficient and reliable operation of the electrical machine. Let's understand why this is the case:

1. **Magnetic Neutral Axis:** The magnetic neutral axis is the axis along which there is no magnetic field in the machine. Placing the brushes along this axis ensures that they make contact with the commutator or slip rings at a point where there is minimal or no magnetic interference. This reduces the chances of sparking and arcing between the brushes and the commutator, which can cause damage to the machine and result in poor performance.

2. **Sparking and Arcing:** When the brushes make contact with the commutator or slip rings, there is a small amount of sparking and arcing due to the electrical current flowing through the interface. This sparking and arcing can lead to wear and tear of the brushes and the commutator surface, reducing their lifespan. Placing the brushes along the magnetic neutral axis minimizes the occurrence of sparking and arcing, thereby increasing the longevity of the brushes and the commutator.

3. **Brush Wear and Tear:** Placing the brushes along the magnetic neutral axis also helps in reducing brush wear and tear. When the brushes are not aligned with the magnetic neutral axis, they may experience uneven wear due to the varying magnetic forces acting on them. This can lead to uneven contact with the commutator or slip rings, resulting in poor electrical contact and increased resistance. By placing the brushes along the magnetic neutral axis, the wear is distributed more evenly, ensuring consistent and reliable electrical contact.

In conclusion, placing the brushes along the magnetic neutral axis in electrical machines is essential for minimizing sparking, arcing, and wear. This ensures efficient and reliable operation of the machine, prolongs the lifespan of the brushes and the commutator, and leads to better performance overall.