Learn Farsi: لامپ آشپزخانه عوض شده است. - The kitchen light bulb has been changed.

You add the negative prefix نـ (na-) to the past participle. In this case, شده becomes نشده (nashodeh). The full negative sentence is لامپ آشپزخانه عوض نشده است (The kitchen light bulb has not been changed).

Why does this sentence use شده است instead of just است?

است simply means is (present tense), but we want the present perfect tense here (has been changed). To do this, we use the past participle of شدن (to become), which is شده, followed by the short copula است. Together, شده است means has become or has been.

I previously learned that to change is عوض کردن. Why do we use a form of شدن (to become) here?

عوض کردن is active, meaning somebody intentionally changes something. Because we aren't mentioning who changed the light bulb, we need the passive voice. In Farsi, you usually make a compound verb passive by replacing کردن (to do) with شدن (to become). So, عوض شدن means to be changed.

Are there any hidden connector sounds (ezâfe) between the words in this sentence?

Yes, there is an invisible ezâfe (-e) linking the first two words, pronounced as lâmp-e âshpazkhâneh. This connects the noun (light bulb) to the place it belongs to (kitchen), literally meaning light bulb of the kitchen.