Computer battery depletion depending on CPU load/app? big machines to phones--add load for 3G, wi-fi

I thought of this as I watched my iPhone tick the last minutes of its life away when I was on-line while riding a bus.

My decision was to quit the net, and–still being bored–switch to iBooks (an internal app) and read books stored locally in the phone.

How much, if any, juice was I saving?

If I had closed the net link, and decided to run my nuclear numerical simulations on my iPhone, would the CPU draw more power?

It also depends on how well the software is written to make use of the particular CPU, and memory architectures?
The governing metaphor in my opening stance stems from this image from any and all cartoons where when someone thinks really, really hard and furiously about something, little whisks of smoke come from their head.

Not too much. Usually the screen is the biggest battery hog that you can easily control. Here is a breakdown of my Android phone’s usage today:

Phone idle: 42%
Android OS: 24%
Display (screen): 14%
Cell standby: 8%
Wi-Fi: 4%

The Phone Idle and Android OS probably are just housekeeping, app updates, things like that, background tasks. It’s worth mentioning that I have my data connection turned off, so Wi-Fi has been on since 8:00 this morning and has only used 4%.

It’s pretty well documented that apps that use GPS to continually update a map will severely impact battery life on smartphones.

To save power in such scenarios, best thing to do is dim the screen brightness, then turn off GPS and all “radios” - WiFi, data (3g, 4g, etc.), and bluetooth. Without doing that, simply switching from surfing online to viewing stuff saved on your phone wouldn’t help a whole hell of a lot.

The people commenting above are correct that the display lighting is one of the biggest battery hits in most phones. But I think they are discounting the cost of RF. It depends what you were doing on the net - were you reading long pages that rarely needed to be refreshed? Or were you often pulling new content down? You definitely would make a different by stopping the net activity. You could save a little more by going into airplane mode, to keep the phone from having to track the network.

I can’t speak for the iPhone, but I fully expect based on other architectures that the CPU runs are varying frequencies, taking varying amounts of power…based on the CPU load. So yes, I’d expect that running your simulations would draw a ton more power than some simple activities.

Yep. At my old job, it was funny when I would start on a new platform, and none of the power management software works. People complain about how hot the phone gets, and how their battery only lasted an hour or two.