The EE is an in-depth study of a focused topic chosen from the list of available Diploma Programme subjects. It is a research essay, 4,000 words long, written in an academic style, and formally presented. The extended essay is described by the IB as a 'major piece of formally presented, structured writing, in which ideas and findings are communicated in a reasoned and coherent manner, appropriate to the subject chosen.'
The aims of the EE are for you to:
engage in independent research with intellectual initiative and rigor
develop research, critical thinking, self-management, and communication skills
reflect on what has been learned throughout the research and writing process
Yes, you should. These are the subjects you know best and have studied the most. You are MUCH more likely to be successful writing an EE in one of your three HL subjects than you are writing an essay in a subject where you have no understanding of the theoretical background, the subject material, the language, or the subject's conventions.
If you really want to write an EE in a subject that you are not studying for the DP, and which perhaps you have never studied, then you must discuss this with the DP Coordinator.
The maximum length is 4,000 words. Examiners are instructed not to read or assess any material in excess of the word limit. This means that essays containing more than 4,000 words will be compromised across all assessment criteria. Given the holistic nature of the assessment criteria, writing in excess of the word limit is self-penalizing. This means that there is no actual penalty for going over 4,000 words, but you are very likely to lose marks by doing so.
There is no minimum number of words, but writing under 3,000 is likely to result in a low grade, as you won't be able to indicate sufficient knowledge, understanding or critical thinking is such a low number of words.
EEs in a group 1 or group 2 language subject must be written in the chosen language. So, an English A essay must be written in English, a Danish B essay must be written in Danish ...
Extended Essays in subjects from groups 3 (Humanities), group 4 (Sciences), group 5 (Maths) and group 6 (Arts) can be written in English, French or Spanish. However, there is an exception for history and biology, which can also be written in German.
BUT, remember that your supervisor will need to be able to read the language in which you are writing your essay - so don't plan on writing a Math EE in Spanish, unless your Math teacher is also a fluent Spanish speaker.
Keep in mind that you cannot write a Danish B extended essay if you are studying Danish A. The rule is Extended Essays in group 2 languages are for learners of a second or an additional language. A candidate is not permitted to submit a group 2 extended essay in the language A that is his or her chosen group 1 subject. Equally, you should not write a Danish A EE if you are studying Danish B. The rule is Extended Essays in group 1 are intended for candidates whose best language is the language A chosen for the extended essay.