Herkese Merhaba!

I had a question about objects in Turkish.

Take a look at these two sentences:
(1) O her yıl araba değiştirir.
(2) Ben sık sık telefonumu değiştiririm

In (1), we use araba and not arabayı, so car in its simple form.
In (2) however, we don´t use the simple form (telefonum) but telefonumu, so "my telephone" is regarded as object, as it should be.

So my question is, why although araba is the object in (1), it is not used as an object? Why don´t we say
O her yıl arabayı değiştirir.

Thank you in advance!

Take a look at these two sentences: (1) O her yıl araba değiştirir. (2) Ben sık sık telefonumu değiştiririm In (1), we use araba and not arabayı, so car in its simple form. In (2) however, we don´t use the simple form (telefonum) but telefonumu, so "my telephone" is regarded as object, as it should be. So my question is, why although araba is the object in (1), it is not used as an object? Why don´t we say O her yıl arabayı değiştirir.

It´s definite/indefinite object thing.

(1) does not indicate a specific car so it is a general talk.

(2) is about a specific thing so it needs (-u) accusative suffix.

O her yıl arabayı değiştirir = He changes (i.e apply changes to) THE car

O her yıl araba değiştirir = He changes cars every year (i.e. buys a new car)

Makes perfect sense, thank you very much for your clarification!

You could just as easily say: "her yıl telefon değiştiririm".

The difference here is that that would translate to "I change phones every year" while your original example is "I change my phone every year".