If you've wondered why your smart phone's battery life seems short, free apps and the advertisements that come with them may be responsible.
A study by researchers at Indiana's Purdue University found running one app can drain a battery in 90 minutes.
Using energy profiling software called Eprof, the researchers discovered 65-75 per cent of the energy used by apps downloaded for free was used by third-party advertises, whose adverts pay for the product.
The study looked at the energy usage popular free smart phone apps, such as the Angry Birds, NYTimes and CNN apps, on Android and Windows Mobile operating systems, and found only 10-30 per cent of the energy was used powering the apps' core functions.
Angry Birds, for example, used only 20 per cent of the energy to run the game, while 45 per cent of the power was used assessing the user's GPS and downloading location-specific advertisement through 3G.