Solar 'death ray'...

[W3LK]

Now it turns out that "multitasking" often means "doing several things poorly at the same time.

That's the best line I have read this week.

[N1DVJ]

And so people got the idea that doing just one thing at a time was old-fashioned. It meant a person was stupid, lazy or both.

Hey, I know of people that can't even read on the toilet without making a mess, so they obviously can't multitask!

[KC8OYE]

I totally agree on the distraction stand point.

i suppose with those ANCIENT dinosaur Motorola StarTac's and brick phones the batteries might have enough power to generate a spark.

but most modern phones even w/o slide off batteries, (I've dropped mine a few times and had the phone go one way, the battery another, and the cover a third..) just don't have enough power at a measly 3v to generate a spark with sufficient energy to ignite gasoline vapors.  Amazingly enough, a cigarette ember doesn't either. (been explored a few times on mythbusters). however.. someone lighting a cigarette with an open flame could get ugly around vapors

I have a video somewhere of a lady gets out, starts pumping gas, and gets back in the car. .when it's done, she gets out, grabs the pump nozzle and a static electricity spark from her hand to the nozzle ignites the vapors... I'm sure that happens a lot more then people realize!  It's wise advice to never get back in your car while pumping.. but in places like here in michigan.. sometimes it's just too DARN cold to stand outside waiting.. especially if you have a big truck and you are pumping 40+ gallons!  so *ALWAYS* (even if you don't get back in the vehicle) touch the pump body FIRST to make sure you ground yourself before grabbing the nozzle!

[STAYVERTICAL]

Even 3V could have enough energy to generate a spark, but it would have to be applied across a load which stores energy, such as a coil, and then the circuit broken.
The same principle is used in automotive ignition systems of dinosaur vintage where 12 volts is impressed across a spark coil, and the distributor breaks the circuit.
The stored energy in the coil and the collapsing magnetic field cutting across the inductor, induces a high voltage which gives us the classic spark when we turn off an inductive circuit.
HOWEVER, most cell phones don't present a huge inductive load to their battery, so this is a non starter.

On solar death rays, they certainly work, but as an energy concentrator for use in solar power stations, employing huge, highly precise and controlled mirrors which boil liquids to drive turbines.
Not exactly a portable solution, but works.

73s

[KC8OYE]

well at the point that you are dealing with collapsing magnetic field, you are no longer dealing with 3v
but I get your point.  and I'm pretty sure most cellphones don't have big inductors.. and with a maximum transmit power of about 1/4 watt.. they don't present much of a current load to the batteries either!