I have an appoved adsense account and I have placed ads on a blog. Now I need to place ads for my second blog also. So Is it neccessary to get approvel for second blog or can I use ads without getting their approval?
no it's not necessary, you should use the same account. But this is written in adsense help pages, is it blocked in sri lanka?
You can use the adsense code on your second blog, third blog and so on as you like, just you gotta ensure none of them against adsense TOS
No. You don't need another approval now. Just put the adsense code in the second blog to display the ads there.
If your Adsense account has already been approved, you can create Adsense codes to integrate into as many sites as you want. Just make sure that none of them violates Google's policies.
You canuse the Same AdSense Account for other blogs. Go to AdSense For Domain after login to your AdSense account and then follow the steps to add your new domain in it..