The correct answer is D. all of the above.
A DC series motor is a type of electric motor that uses a DC electric current to power a rotating magnetic field. The magnetic field interacts with the windings of the motor to create a torque that turns the motor shaft.
When a DC series motor is operated on an AC supply, the current will alternate in direction. This will cause the magnetic field to alternate in direction, which will cause the motor to vibrate and spark excessively. The alternating current will also cause the motor to have poor efficiency and power factor.
The following are some additional details about each of the options:
- Option A: Spark excessively. When a DC series motor is operated on an AC supply, the current will alternate in direction. This will cause the magnetic field to alternate in direction, which will cause the motor to vibrate and spark excessively. The sparks can cause damage to the motor and create a fire hazard.
- Option B: Have poor efficiency. The efficiency of a motor is a measure of how much of the electrical energy it consumes is converted into mechanical energy. When a DC series motor is operated on an AC supply, the alternating current will cause the motor to have poor efficiency. This is because the alternating current will cause the motor to lose energy in the form of heat.
- Option C: Have poor power factor. The power factor of a motor is a measure of how efficiently the motor converts electrical energy into mechanical energy. When a DC series motor is operated on an AC supply, the alternating current will cause the motor to have poor power factor. This is because the alternating current will cause the motor to draw more current than it needs to produce the same amount of mechanical power.
In conclusion, if a DC series motor is operated on an AC supply, it will spark excessively, have poor efficiency, and have poor power factor.