Which of these will increase with an increase in the number of poles?

With an increase in the number of poles in an electrical machine (such as a motor or generator), the following characteristics will increase:

1. Torque Capability: Generally, an increase in the number of poles in a motor can lead to an increase in its torque capability. This happens because the torque of a motor is directly proportional to the magnetic flux, which can be increased by having more poles.

2. Magnetic Field Strength: More poles contribute to a stronger magnetic field within the machine, assuming all other factors like current and material are kept constant.

3. Frequency of the Output Voltage (for Alternators/Generators): In AC generators or alternators, the frequency of the output current is directly related to the number of poles and the speed of rotation. An increase in the number of poles at a constant speed will lead to an increase in the output frequency.

However, it’s important to note that while some aspects increase with more poles, the overall speed at which the machine operates (synchronous speed in electric motors, for example) decreases. The formula for the synchronous speed of an AC motor is ( frac{120 times frequency}{number of poles} ), showing that the speed decreases as the number of poles increases, assuming the frequency is constant.