Is this translation right?
 

I have to translate: "Today is the day of the physics exam":
kyou wa butsurigaku no shiken no hi desu
is this right?

"Kyou wa butsurigaku no shiken ga aru" might sound more natural.

I'm not sure what the context is that you're working with, but if you're looking for a natural way to say it, I would replace "butsurigaku" with just "butsuri." I studied physics with Japanese people in college and in my experience everyone refers to it as just "butsuri."

If I were having a conversation with somebody, I would just say, "Kyou wa butsurigaku no shiken desu ne"

That sounds like "Today's a physics exam, huh?"

Should be 今日は、ぶつりがくの　試験　がある。 Luc, your sentence is technically correct, but it's a bit awkward. I think the ones we've suggested are a bit more natural sounding

True, but I hear phrases like this all of the time. "Today" is just the time frame, so "wa" doesn't necessarily mean you're making "today" equal something. Just like how you say, "Kyou wa ame ga furu," you don't literally mean, "Today is falling rain." I hope that explanation made sense...

Yeah, somehow saying "there's a test today" with that grammar just didn't feel right. But maybe you're right and I'm wrong!

I could be wrong too, but something tells me it's atleast "okay" to use it in this sense.

I'm confused as to why an "expert" hasn't shown up to sort out this little ordeal here. I hope it isn't too simple that it's beyond their knowledge ;]

That is called Ellyptical construction (or something like that). It exist when a big part of the phrase is already known and thus it is cut off and the です part will substitute it. But I don't think you can use it from "scratch", without having introduced the topic previously.
I will try to do an example.
レストランで。
ボブ：僕はてんぶらを食べたい。お前は？
ジム：僕はすしだ。
Literally it means I want to eat tenpura and you? The answer doesn't mean "I am sushi", but it means I want to eat some sushi. In this form what the phrase actually should be is: 僕の食べたいことはすしだ (the thing I want to eat, is sushi).
As you can understand if I come up to you and all of a sudden I start saying 僕はすしだ it really makes no sense and you would call a shrink for me. It all has to do with what was said previously.

(Always wait for a native to confirm this, I will never get tired of saying it).

This translation is correct, both grammatically and literally.

BTW, I find all the other examples given by the others are correct as well. It all depends whether you want it translated word-for-word or words to that effect.

By saying it orally, there are a variety or ways to relate the same thing. It all depends on the mood of the speaker, the relationship between the speaker and the listener, etc.