Reputation
4,049
Next privilege 5,000 Rep.
Approve tag wiki edits
Badges
1 11 28
Newest
 Yearling
Impact
~231k people reached

Jan
19
reviewed Approve Why mass can distort spacetime?
Jan
19
reviewed Approve Charging by induction
Jan
19
reviewed Approve Help with Gravity question
Jan
17
comment Is equivalent resistance always lower if we add a resistor to a passive electronic circuit?
Very nice approach! I think, though, that you overreach a bit when you state: "The product is definitely positive". It is entirely possible that v1=0; consider the example of a balanced bridge mentioned by Emilio Pisanty in a comment above.
Jan
15
awarded  Enlightened
Jan
15
awarded  Nice Answer
Jan
14
reviewed Reject How to perform a rotation of field of view using only mirrors/lenses?
Jan
14
reviewed Reject EM Wave equation and dispersion in a plasma
Jan
13
reviewed Reject Given a light diffracting through an aperture of radius r, how would we find the radius of the beam at a position x meters away?
Jan
12
reviewed Approve Moment of inertia meaning?
Jan
8
reviewed Approve Why does the QCD vacuum have zero momentum?
Jan
8
reviewed Reject Uniform Electric field cannot propagate a wave of finite wavelength?
Jan
8
answered Deriving the Lienard-Wiechert Potentials
Jan
7
reviewed Reject how can we reduce the temperature below -60 degree celsius?
Jan
2
reviewed Approve Variation of a tensor
Jan
2
reviewed Approve Semi conductors (holes and electrons)
Dec
29
reviewed Approve How do electrons move across depletion region in npn transistor?
Dec
27
answered From Liénard-Wiechert to Feynman potential expression
Dec
27
comment Help me understand eqn. 28.6 from Feynman
@TolgaYilmaz, (ii) When I calculate that second derivative of the unit vector (which I did a while ago, taking a very long time to work through it), the result is complicated, and in fact is non-zero even if the acceleration $a'=0$. What I wrote in my answer was only approximate (good at low velocities and large distances). However, Feynman's expression (28.6) for the electric field is exact: I was able to show its equivalence to the results in Jackson's and Schwartz's textbooks.
Dec
27
comment Help me understand eqn. 28.6 from Feynman
@TolgaYilmaz, (i) If you're referring to the units, the convention is the vector $\boldsymbol{r'} =|\boldsymbol{r'}| \boldsymbol{e}_{r'}= r' \boldsymbol{e}_{r'}$, so $\boldsymbol{e}_{r'}$ is unit-less.