There are a lot of so-called 'IQ tests' being put on the web which are really quizzes and these include the type of general knowledge questions that you mention.
A proper 'Mensa' IQ test that is done under controlled conditions and supervision has none of that type of general knowledge question. Much of the test consists of sections containing shapes and patterns and asks which shape would follow this one or which ones go together etc. Then there are the mathematical teasers that try and confuse the brain. The type of questions asked are abstract and are often not dependent on whether you 'know' the answer, you often have to 'sense' the answer. There's a lot of lateral thinking required and you certainly don't have to be 'good' at IQ tests or not. They are not like taking an exam where you will have studied the subject.
I was invited to take an official Mensa test a few years ago and consquently went down to the University of London and sat in a classroom with a varied group of adults and we all nervously took our places and opened our test papers. Each page could only be opened at a certain time and some of them had questions on the reverse and some didn't. Once a page had been completed, you couldn't go back and add or change anything. It was quite an experience!
It turned out that I wasn't a genius after all (hehehe..... I knew that anyway!) but I did fall into the top 5% of the UK population with an IQ of 138. I wasn't invited to join Mensa either - that privilege is reserved for those who come out within the top 3% of the population.
But it was quite interesting all the same!