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comment What does it mean by “infinities” when dealing with quantum mechanics?
"What kind of infinities are there that discovering renormalization was such an impressive feat?" - an oldie but goodie: The Second Creation: Makers of the Revolution in Twentieth-Century Physics. Chapters include "Killing the Hydra (Part 1)" and "Killing the Hydra (Part 2)"
14h
answered Why is capacitance defined as charge divided by voltage?
18h
comment How do we get 25kV at power stations?
@justin, CuriousOne has given you all the ingredients. It's up to you to bake the cake.
1d
comment self-inductance, back-emf
I've always thought a balloon was pretty good analogy for a capacitor (with one plate grounded). The pressure is analogous to voltage and the flow of air is analogous to current. For an inductor, however, I've considered a ducted fan with some moment of inertia. Changes in the flow of air (or other fluid) through the duct are opposed by the fan by creating a pressure that opposes the change.
1d
answered self-inductance, back-emf
1d
comment self-inductance, back-emf
The negative sign is there in Maxwell's equation: $\nabla \times \mathbf{E} = -\frac{\partial \mathbf{B}}{\partial t}$ and the inductor equation must be consistent with this. Or are you asking why the negative sign in this equation?
1d
comment What happens if I slowly lower a dangling object into a black hole?
"But if I lower it just below the event horizon" - you can't observe the object crossing the horizon.
1d
comment What happens if I slowly lower a dangling object into a black hole?
"so the person pulling from far away doesn't detect anything different either" - but it also true that the proper acceleration of the dangling object hovering above the horizon is unbounded as $r \rightarrow 2GM$.
1d
comment Centripetal force: if radius decreases, does ANGULAR or TANGENTIAL velocity change?
@Frobenius, your comment is essentially an answer and the core of a good 'official' answer. As to whether this question is considered off-topic by some, I don't care. If you find it of value to compose and post a genuine answer, then do it. It might be that others find it valuable too.
2d
comment Centripetal force: if radius decreases, does ANGULAR or TANGENTIAL velocity change?
Do we have to say something like "the string is pulled uniformly" so that the puck has no radial acceleration? Also, since the speed of the puck is increasing, the velocity vector and force vector cannot be perpendicular can they?
2d
comment Centripetal force: if radius decreases, does ANGULAR or TANGENTIAL velocity change?
@Frobenius, shouldn't that be an answer?
2d
answered Solenoid vs coil of wire
2d
reviewed Approve Centripetal force: if radius decreases, does ANGULAR or TANGENTIAL velocity change?
Apr
25
revised How do we know the Schwarzschild solution contains an object of mass $M$?
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Apr
25
answered How do we know the Schwarzschild solution contains an object of mass $M$?
Apr
24
revised State why the value of the internal resistance of cell $B$ is not required for the determination of $E$
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Apr
24
answered State why the value of the internal resistance of cell $B$ is not required for the determination of $E$
Apr
24
revised Why current in series circuit is the same?
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Apr
24
answered Why current in series circuit is the same?
Apr
24
comment Why current in series circuit is the same?
If you have a resistor in your series circuit, then the current is reduced" - This isn't necessarily true. For example, adding a resistor in series with a current source will not reduce the series current.