581 reputation
27
bio website
location Sandy Eggo
age 57
visits member for 2 years, 3 months
seen Jun 20 at 6:01

Know lots about GPS and other positioning technologies, lots about cellular air interfaces. Pretty new to Java/Android. Lots about Electromagnetics and Physics (Physics PhD, used to teach Electrical Engineering at University). Fair amount about superconductivity.


Jun
8
comment Maximum theoretical efficiency of internal combustion engine
@Simon yes gasoline routinely heats things up much higher than its combustion temperature. Combustion temperature is threshold for oxidation, but heat released by oxidation can easily heat things to many times that temperature.
May
9
awarded  Scholar
May
9
accepted Why does hydrogen give up its electron to a platinum catalyst?
Apr
30
comment Suggest why electrical power input P1 differs from power used P2
You didn't heat just the water, you also heated the heating coil. That is, you brought the 200 ml of water from T1 to T2, but you also brought the heating element from T1 to T2, which also takes energy.
Apr
30
comment Suggest why electrical power input P1 differs from power used P2
If heating element resistance RH and wire between power supply and heating element resistance RW, current from power supply I, then you are drawing power $I^2(RH+RW)$ but only putting power into water of $I^2RH$. Since heating elements tend to have low resistance, it would not be too hard to have a situation where 1/3 of all your energy was lost in the wire between power supply and heating element.
Apr
30
answered Does a photon travel through space exactly at the speed of light?
Apr
30
comment Why does hydrogen give up its electron to a platinum catalyst?
Every picture I see does NOT show H or H2 being adsorbed on the platinum anode, but rather the electron from the H going in to the platinum anode and the $H^+$ running away from the platinum so it can diffuse across the membrane and show up at the cathode.
Apr
30
asked Why does hydrogen give up its electron to a platinum catalyst?
Apr
23
awarded  Yearling
Apr
23
awarded  Yearling
Feb
11
asked Force of electromagnet on piece of iron
Nov
29
awarded  Caucus
Oct
4
answered What color would a proton be if it were visible to the human eye?
Sep
3
comment Does the uncertainty principle apply to photons?
@genneth of course you are right, I was wrong about why you are allowed to "violate" ∇⋅E=0, which is of course because $\nabla E=\rho/\epsilon_0$. So at time t=0 some charge shows up at the origin creating a delta function of electric field at the origin, and then run time propagation from there.
Aug
30
comment Does the uncertainty principle apply to photons?
@genneth ∇⋅E=0 is a static constraint, I am not talking about static fields. I am talking about an initial condition at time $t=0$ which will not be static at t>0. Every light beam and radio wave we know of violates ∇⋅E=0 in free space.
Aug
27
answered How come a photon acts like it has mass in a superconducting field?
Aug
27
comment Does the uncertainty principle apply to photons?
@dushya Consider an electric field in the $z$-direction at time 0 $E_z(x,y,z,0) = $\delta(x)\delta(y)\delta(z)$. It is a straightforward matter to calculate "classically" (and result is correct for quantum) the $E_z(x,y,z,t)$. You will never detect a photon at $r>ct$, the photons are localized inside the appropriate light-sphere. Please describe what is meant by "photons cannot be localized" in light of this simple experimental fact.
Aug
27
comment Does the uncertainty principle apply to photons?
@genneth There is no difference between light and electrons in anything you are saying, except it is very rare we see electrons coming from a source smaller than electron wavelength because electron rest mass makes its wavelength very small. A pulse of light 1 ns long is 30 cm long and is completely localised throughout its entire time of flight, you can put things in its path before and after it passes without stopping it, but put something in its path while it is passing and you stop the beam.
Aug
27
comment Does the uncertainty principle apply to photons?
@genneth can you give me a reference that goes beyond a single sentence saying it can't be done? I'd love to understand how a photon represented by a wave packet is any different from an electron represented by a wave packet.
Aug
26
comment Does the uncertainty principle apply to photons?
@AlecS I can't read the PRA ref, don't have login. In the google docs ref, what you cite is an unpublished one line quote from a referee of the paper. I call B.S. on the referee, and challenge you or anyone else to find a sensible refutation to what I say about localization.