Investors will be listening intently today when Apple CEO Tim Cook addresses the Goldman Sachs Technology and Internet Conference. The tech giant’s stock is on a tear — it closed Monday at $502.60, a record high and up 24.1% so far in 2012. And Wall Street is trying to figure out: Is this run up just beginning, or is it time to sell? Cook could provide some clues in the way he handles questions about investors’ extravagant expectations for Apple’s efforts to introduce new or refreshed products this year. It’s widely believed that early next month it will unveil the iPad 3, with a sharper screen and the ability to tap Verizon and AT&T’s 4G wireless networks. Now it seems Apple also is testing a tablet with a smaller, 8-inch screen to take on rivals such as Amazon’s Kindle Fire, which has a 7-inch screen, The Wall Street Journal reports today. Meanwhile bulls say that the iPhone will continue to be a big story this year with sales just beginning in China — and the widely expected release in the U.S. of a 4G-capable iPhone 5. Apple also is benefitting from the business market’s deteriorating faith in Blackberry phones as the company behind them, Research In Motion, grapples with the corporate turmoil that resulted in the replacement last month of its CEO. For example, Halliburton recently said that it’s switching its employees to Apple phones. And of course there are multiple reports that Apple hopes to revolutionize the television set market — and perhaps television itself — with a device that can blend content from conventional programming sources and the Web and still be easy to navigate. Remember: Some of these expectations could be wrong, or overly optimistic. Apple also would take a hit if human rights activists find additional evidence that workers are being abused at the factories in China that make the company’s products. Yesterday Apple said that the U.S.-based Fair Labor Association will investigate the situation.