A report to be released Thursday says more and more Americans are using mobile devices to connect to the Internet. Usage of smartphones and tablets to check email, browse the Web, and log on to social networks is up sharply, the Commerce Department’s National Telecommunications and Information Administration has found. The NTIA report is based on a U.S. Census Bureau survey of more than 53,000 households. Between July 2011 and October 2012, the percentage of Americans who used mobile devices to access the Internet jumped: Downloading mobile apps increased to 32 percent from 22 percent, browsing the Web to 42 percent from 33 percent, checking email to 43 percent from 33 percent, and logging in to social networks to 30 percent from 22 percent. Those with higher income and education levels are still more likely to use mobile devices to access the Internet, the study found.