Option 1: Generator
A generator is a device that converts mechanical energy into electrical energy. It uses a rotating coil and a magnetic field to produce an alternating current. However, a generator does not change low voltage alternating current to high voltage alternating current or vice versa. Therefore, option 1 is not the correct answer in this case.
Option 2: Motor
A motor is a device that converts electrical energy into mechanical energy. It uses the interaction between a magnetic field and current-carrying conductors to generate a rotational force. A motor does not change voltage levels, so option 2 is also not the correct answer.
Option 3: Transformer
A transformer is a device that changes the voltage level of an alternating current. It consists of two coils, called the primary and secondary windings, which are magnetically coupled. By varying the number of turns in the coils, a transformer can step up or step down the voltage level of the alternating current. Therefore, option 3 is the correct answer in this case.
Option 4: Vibrator
A vibrator is not a device used for changing voltage levels in an alternating current. It is typically used in mechanical devices to generate oscillations or vibrations. Therefore, option 4 is not the correct answer.