What happens when the magnetic field consists of two poles?

What happens when the magnetic field consists of two poles?

• A. Induced voltage becomes zero
• B. Induced voltage remains constant
• C. Induced voltage increases linearly
• D. Induced voltage switches polarity once per revolution

Answer: (D)

With a two-pole magnetic field, the flux seen by a fixed coil changes direction as the rotor moves from facing one pole to facing the other and then back again. The induced voltage in the coil is tied to how fast the flux is changing; when the pole swaps, the flux direction reverses, so the polarity of the induced voltage reverses as well. Because there are just two poles, this reversal completes over one full turn of the rotor, meaning the output voltage completes one full AC cycle per revolution. In other words, as the rotor turns once, the polarity at the output switches once, producing the alternating waveform associated with a two-pole machine.

With a two-pole magnetic field, the flux seen by a fixed coil changes direction as the rotor moves from facing one pole to facing the other and then back again. The induced voltage in the coil is tied to how fast the flux is changing; when the pole swaps, the flux direction reverses, so the polarity of the induced voltage reverses as well. Because there are just two poles, this reversal completes over one full turn of the rotor, meaning the output voltage completes one full AC cycle per revolution. In other words, as the rotor turns once, the polarity at the output switches once, producing the alternating waveform associated with a two-pole machine.