Recent content by User11037

Homework Statement Apply Kirchhoff's laws to find the current at point X in the circuit shown. What is the direction of the current? Homework Equations V = IR Kirchhoff's 1st law: ∑Currents entering junction = ∑Currents leaving junctions Kirchhoff's 2nd law: ∑EMFs in a loop =...

Hi, With permanent magnets I have been puzzling over how they can obey the conservation of energy. If I make a permanent magnet then I can use it, expending negligible energy myself, to attract, and thus give kinetic energy to, many other metallic objects. So, when I create my magnet...

Hi, this is probably a silly question but I can't seem to find the answer anywhere: are the effects of relativity calculated with reference to the speed of light in a vacuum or the speed of light in the medium in which you are traveling? For instance, if traveling in water, would the Lorentz...

But, why is it valid to say that during my trip the star is aging and I am not, but not to say that I am aging and the star is not. Surely the two situations are symmetric?

But surely that's a contradiction, because the star is emitting light at a constant rate and this light will always travel at the speed of light, regardless of my speed, I must continue to see the star age at its normal aging rate? Also, I just thought, if you model it as the star moving...

But, that would imply that, while I am traveling, I would see the star ageing at twice its normal rate?

Time Dilation Surely time dilation would have an effect?

It is often quoted that, when we see stars from Earth through, for example, a telescope, we are not seeing them as they are now, but how they were millions of years ago (because the travel of light is not instantaneous). However, say if I take a picture of a star from Earth, then jump into a...