all of the words you wrote would be correct with W. some people pronounce W as V with their personal accent, varies by region and it's rather a dialect instead of standard mandarin.

Laurence, I know exactly what you mean. Here is what I think: 1. It is not a matter of dialect. Even if we take the pronunciations of a broadcaster or an actor with a standard accent, the way that he does w in 我 is quite different from the way he does w in 威。 2. You have correctly spotted a real difference. 3. In fact, the Chinese w, whether in 我 or in 威, requires the lips to be positioned differently from the white Anglo Saxon w. 4. The w in 我 starts from much more of a "kissing fish" lip position, in order that the finishing o may be pronounced fully (说得满) and correctly. At the starting position of 我, the lips are pushed much more forward than the English w. This w is much more exaggerated than the English w. 5. The w in 威 starts from a more retracted lip position that is akin to the English v lip position EXCEPT that the upper teeth do not extend over the lower lip. The amplitude of the lip movement from start to finish us much smaller than in 我. This w is much more restrained than the English w. The "ei" sound of 威 is also pronounced from a much more compressed mouth cavity than the English "way". The English "way" is pronounced much closer to the throat. The Chinese "wei" finishes right in the middle of the mouth cavity. This finishing position of the Chinese "wei" means that the starting consonant of w is less overtly forward in order for the finish to be sufficiently compressed, with the finishing "i" ("ee" in English) quite fully pronounced. 6. We have to bear in mind that the English alphabet is a "transplant" that has been grafted onto Chinese sounds. In an ideal world, there should be two different symbols for the two starting consonants of 我 and 威, and neither of these should be the English w. 7. You are already ahead when your ears and eyes are good enough to have spotted the physical sound difference, though on paper it is the same w.

Definitely have heard this with 玩儿 with one of my language partners and in language tapes I have which are supposed to be Beijing accent. Pretty sure it depends on the local accent, and keep in mind that many Chinese might not even notice. Think about the stereotypical German accent pronouncing w as v, in part because they don't have a v sound in that language (in addition the spelling). I think W and V sounds are hard to distinguish if your language doesn't have both. Neither pronouciation is "wrong" any more than American English or RP English are "wrong". (For those who aren't sure what a V or W sound are, look them up on the IPA chart on wikipedia. The letters are the same as in English, but the W will be in one of the extra boxes)

That has something to do with the dialect. Some Chinese people don't distinguish 'W' with 'V', as there is no the [V] sound in Chinese Pinyin. In fact they are different. When you want to pronounce 'V', you should put lower lip under your upper teeth and sometimes your upper teeth should bite your lower lip slightly. As for 'W' sound, you don't do so.

(continuing from above) 8. You will one day speak perfect Putonghua. You now need to ensure that you practise Putonghua with people who have the best accent. That means picking your friends and tutors. 9. On the question of accent, which is highly sensitive and emotional for a lot of native Chinese speakers, we can have another dialogue out of the public glare.