When it is plugged into a wall outlet, the alarm clock lights up with a time display. What kind of energy transformation takes place?

The energy change taking place in the clock is the electrical energy to the mechanical energy to the light energy.

Explanation:

The alarm clock will work in the battery in the form of electrical energy. Then due to the current passed the electric motor rotates the blade. Then the energy is converted into mechanical energy. Then the mechanical energy generates the light and When it is plugged into a wall outlet, the alarm clock lights up with a time display. This is the energy transformation taking place in the alarm clock.