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Saturday, March 31, 2012

A 'Boy Wonder' Tackling Nuclear Science

Check out this video about Taylor Wilson, who at age 17 has already taught a graduate level nuclear physics course, has built a small fusion reactor, and invented a cheap way of detecting nuclear materials in shipping containers for national defense purposes. He appears to be that rare, nearly once a generation type prodigy/genius who is making a difference while very young.

Saturday, March 17, 2012

RL Circuit with Resistor and Inductor in Parallel

Here is a circuit where a resistor and inductor are in parallel with each other. This is similar to a RC circuit with a resistor and capacitor in parallel. We focus on t = 0 and a 'long time.'

The gist of this one is that inductors fight current initially because they do not like a change in magnetic flux. After a long time, an inductor is just a piece of wire with no resistance (at least for us!). Check it out.

How to Find Terminal Velocity of Conducting Loop Falling into B-field

Here is a different type of induction problem. This has to do with the long aluminum tube we have in the lab, and even though it is non-magnetic, a falling magnet in the tube falls with a terminal velocity. Huh?! The reason for this is as the magnet moves, it is changing flux in the loop. This induces a voltage (Faraday) and therefore a current (Ohm). In a tube these are called eddy currents.

But those currents then feel a force since they are in a magnetic field. This is F = Il x B. The force is upward, trying to stop the motion and therefore stopping the change in flux (Lenz). The mathematics turn out to be identical to that of a sky diver with air friction! We will get an exponential solution, and a terminal velocity. Check it out!

Friday, March 16, 2012

New Neutrino Results from an Independent Group - Einstein was Right

Results from a European research team called Icarus show that neutrinos do not move faster than light. The team is headed by Carlo Rubbia, who is a Nobel Prize winning particle physicist and former director of CERN. Icarus is a similar experiment to OPERA, which is the group that had measurements of neutrinos above the speed of light. Recent information from OPERA suggests the possibility that their measurements could be off due to some poor pieces of equipment in the experiment.

This is a wonderful example of how science works. One must have some thick skin at times, because when you publish results of any experiment, by definition it must then undergo the scrutiny and questioning of the community. Peer reviewed articles, reproducible experiments that can be tested and looked at independently, debate, talks and conferences, and so on, all provide opportunities for scientific world to question your work. It is necessary to be skeptical. It is necessary to keep an open mind. It is necessary to listen.

We will see how this continues to unfold and proceed, but it is interesting to watch and learn.

Leading Climate Scientist James Hansen - TED Talk

James Hansen is perhaps the leading climate scientist in the world. Check out his thoughts, as well as evidence for climate change, in this TED talk. This is a crucial issue for future generations.

TED Talk by Adam Savage (Mythbusters) - Simple Ideas Lead to Discovery!

Adam Savage of MythBusters fame, talks about how some simple ideas have led to great discoveries in science that have changed the world. I found it interesting, so enjoy and let me know what you think!

Tuesday, March 6, 2012

How to do Biot-Savart for Loop of Current

A second example of Biot-Savart is with loops of current. We know that any current will produce a magnetic field, but a circular loop of current produces a linear magnetic field along its central axis. This is like the Helmholtz coil we use in the lab. Check out how to set this up and get an expression for that central axis.

How to do Biot-Savart for Straight Wires with Ends

We have done some work already with Ampere's law for finding B-fields created by long wires, solenoids (with no ends) and toroids. But in reality wires have ends, and we must use the real thing, Biot-Savart, to get those magnetic fields. Check this out for finding the integral for a straight wire with ends.

Hacking into just about anything wireless - consequences of a wireless society

Check out this TED talk about how hackers can get into just about anything electronic and wireless. This is, in my mind, one of the great concerns for now and forever into the future. Electronic security systems are developed everyday, but it is a matter of time before hackers find a weakness to be exploited. Then the next newest, best security system is designed, only to be hacked in time. And so the game goes.