what are differences between " in case" and "in case of"

[chibi]

There is a sentence like that: "if there is an emergency, ring this number"
it can change into: "in case of emergency, ring this number." ( remember starts with in case)

But why is the sentence "in case, there is an emergency, ring this number" incorrect?

could you please explain for me?

[David L.]

But why is the sentence "In case, there is an emergency, ring this number" incorrect?

Take out the comma after 'case' and it is quite correct:
"In case there is an emergency, ring this number."

Perhaps you are confusing this with:
He: I've got enough money on me for the movies.
She: Just in case, you'd better take this extra £10.

[chibi]

But why is the sentence "In case, there is an emergency, ring this number" incorrect?

because this sentence is in a test for good students. When my friend did " in case, there is an emergency, ring this number", she hadn't got mark.

there is another example with in case:
I'll take this umbreller because it may rains
=> in case it rains, I'll take this umbreller.

I think, maybe I'll take this umbreller will be real , and these is an emergency can be real or not. That is just small difference I can find. However, it is not enough to explain for my question.

:D thank you very much for your explaination

[David L.]

No, it is not to do with whether a situation is real, imagined or conjectured.

In that sentence, the phrase is, 'in case of...', so to mark of 'in case' with a comma is incorrect - it separates the phrase into 'in case' and 'of'.

'I'll take this umbrella in case it rains.'

[thanhthanh.esl]

because this sentence is in a test for good students. When my friend did " in case, there is an emergency, ring this number", she hadn't got mark.

there is another example with in case:
I'll take this umbreller because it may rains
=> in case it rains, I'll take this umbreller.

I think, maybe I'll take this umbreller will be real , and these is an emergency can be real or not. That is just small difference I can find. However, it is not enough to explain for my question.

:D thank you very much for your explaination

Theo ý kiến của mình, thì : in case of + N/phrase hoặc in case + clause có thể giống như nguyên nhân- kết wả vậy ( vì e rằng trời mưa nên tôi mới mang theo dù) vì thế chúng lun đi kèm với nhau, Còn khi in case đứng riêng , chỉ dùng khi bạn ngầm hỉu rằng nguyên nhân đã đc biết trước rồi ( như đoạn đối thoại của 2 người ấy )
Hì,nghĩ sao thì mình nói thế thôi, hy vọng bạn đừng giận nếu thông tin của mình ko chính xác nhé !