This is a principle about power station: at this time, motor A is a generator (because it converts mechanical energy into electrical energy), and we can think of it as a battery; And we have to think of motor B as a resistor that is easy to cause short circuit (note 1: To know the reason, let's answer it below, and answer the whole working principle first). Turn on the switch (that is, provide kinetic energy to the motor A), but because the motor B is short-circuited, the current increases, and part of the electricity that should have been provided to the motor B will flow back (because A is also a motor and has electric energy, it will naturally produce mechanical energy to compete with the mechanical energy that is being provided to the motor A), which will affect the total current of the circuit and the force exerted on the motor A, and may burn wires or cause the motor to catch fire.

Note 1: This is the principle of the motor, because the current will react with the magnet in the motor and make the magnet rotate. However, when a force stops the magnet from rotating, the current will treat it as a wire, that is, it will not consume its own energy here (not without consumption, but not much). Therefore, in our life, we will find that if the fan blade is stopped by hand or it rotates, the fan will heat up (short circuit feature).